Un-BEE-lievable: The Buzz on Native Bee Conservation in Canada

Guest post by University of Toronto-Scarborough MEnvSc Candidate Rachel Siblock

Unless you’ve been living under a rock (much like native mining bees in Canada), you’ve probably seen the numerous campaigns to “Save the Bees”. Bee species across the globe are in decline. There are many factors that contribute to this decline, such as pesticide use, colony collapse, disease, habitat loss, and climate change¹. Many of these factors interact with one another, exacerbating the consequences and impacts. Conservation efforts are being implemented to try to stop the loss of these pollinators, and the valuable services they provide to humans. Canada is no exception. There are local, provincial, and national policies and programs operating and currently being developed in order to reduce the impacts of these threats. In the past few years, programs like The Bee Cause, Bees Matter, Feed the Bees, and others have implemented programs and recommendations in order to increase the bee populations in Canada. Honey Nut Cheerios has even campaigned to get the public engaged and involved in the conservation of bees. These programs, however, all have one common issue: they focus their efforts on Honey Bees. 

An example of a campaign by Honey Nut Cheerios, focusing on honey bees. 

There are no native honey bees in Canada. The most well-known bee in Canada was not even present in the country until it was introduced from Europe in the 1600s². The European Honey Bee was intentionally introduced to Canada for honey production, and since has increased in number dramatically, both in farmed and wild colonies. Honey bees have large colonies, allowing them to be easily managed and farmed. They also pollinate crops and produce honey, which may make them seem more economically valuable than their native, non-honey-producing counterparts. However, there have been unexpected impacts of the introduction of the European Honey Bee on native bee species in Canada.

            There are over 800 native bee species in Canada. While there are many different types of bees in Canada, the best understood group of native bees are bumble bees. Bumble bees have the ability to buzz pollinate, which allows them to obtain pollen from plants with pollen that is difficult to extract. Many of these plants are economically valuable, such as kiwi and blueberry crops. This, along with general pollination, makes managed populations of bumble bees worth several billion dollars annually³. Bumble bees naturally have low genetic diversity and can be subject to inbreeding depression, leading to declining populations and making the some species more vulnerable to extinction⁴. Threats can then interact with these low population levels, and intensify population loss. 

A male Rusty-patched Bumble Bee, one of Canada’s native bee species. It is currently listed as endangered in Canada.

Aside from facing the same threats as honey bees, native bumble bees are also threatened by the very presence of honey bees. Competition for resources with honey bees is a major threat to native bumble bees. A study performed in the United Kingdom found that bumble bees at sites with high honey bee density were significantly smaller in body size when compared to their relatives at sites with low honey bee density⁵. An additional study discovered a reduction of native bumble bee colony success when colonies were experimentally exposed to honey bees⁶. Honey bees generally produce larger colony sizes which can store a larger amount of resources than bumble bees. They also have the ability to communicate with one another about valuable floral resource locations⁷. Honey bees have a larger foraging range than native bumble bees, and have an increased ability to forage on introduced plant species⁷. These adaptations allow honey bees to outcompete native bumble bees, and commandeer sparse resources in the area.

            Threats from honey bees do not just end at competition; pathogens and parasites specifically adapted to honey bees have been shown to have the ability to spread to wild bumble bee populations. Managed honey bees are known to carry higher than natural levels of pathogens⁸, which can be transmitted to wild bumble bee populations when the bees interact. In particular, two pathogens endemic to honey bees, C. bombi and N. bombi, are wreaking havoc on bumble bee populations. While these pathogens do not have lethal effects, their sublethal effects can be devastating to colonies. These pathogens cause reduced pollen loads, a decline in flowers visited per minute, slower growth rates of colonies, decreased queen reproductive rates, shortened life spans and diminished colony growth⁸. With small populations already, entire bumble bee colonies can be wiped out by these pathogens. Honey bee parasites, such as the Small Hive Beetle, have also been shown to be able to spread to bumble bee colonies, where they consume the wax, pollen, and nectar stores of hives⁸. While honey bees have co-evolved with these parasites and pathogens for eons, bumble bees have not had the time to adapt to these threats, making them much more vulnerable to these hazards. 

Small Hive Beetle infestation in a honey bee colony. 

But why do we care about losing native bees? The same concerns about the loss of honey bees applies to native bees. Native bee species pollinate crops and flowers, which we depend on for food. It is estimated that about one in three bites of food we consume can be traced back directly to pollination by bees and other pollinators. However, native bees have been found to be more effective pollinators than honey bees. Some plant species in Canada rely solely on native bees for their pollination. With the loss of native bees, these plants will also become endangered, along with many other food crops requiring pollination. Additionally, there is a severe lack of research into native bees. Research tends to focus on honey bee populations, resulting in much more knowledge of honey bee behaviours, adaptations, actions, and responses to stressors. The truth is, we don’t know much about native bee species in Canada. We have no idea what the consequences of the loss of these species will be. However, this does not excuse us from protecting these bees. If anything, this lack of knowledge should increase our urge to protect them, so we have the opportunity to learn about them in the future.

            The native bee species in Canada share little life history traits with the European Honey Bee⁸, making many conservation efforts that focus on honey bees unsuccessful. Focusing conservation efforts on one species may not address the specific needs of native bees. In addition, by focusing on improving honey bee populations, there will be increased stress on native bees, which will lead to a decline in their populations. If we continue with these conservation strategies, we may threaten native species further.

            An increase in honey bee populations will increase parasite and pathogen levels in native bees, and also increase the competition between honey bees and native bees. So what can you do to focus conservation efforts on native Canadian bees? For starters, avoid the use of pesticides, which will decrease already low populations⁸. Improve your knowledge of bee species, and report invasive or introduced species in areas used by native bee species. Plant a wide variety of native plants with high pollen and nectar concentrations to ensure newly emerging bees have the resources they need to survive. And finally, avoid tilling, mowing, or burning in areas where native bee species, particularly ground dwelling species, are known to live. With increased knowledge of native bee needs, and species specific conservation efforts, it is hoped that native bee species will begin to rebound. Let’s BEE positive!

BEE Informed – To get involved with native bee conservation check out these links:

Native Pollinator Initiative – Wildlife Preservation Canada

Bumble Bee Recovery – Wildlife Preservation Canada

Help Native Bees – Conservation Halton 

Native Bee Information – Canadian Wildlife Federation

BEE-bliography:

    1.     Pettis, J.S., and K.S. Delaplane. 2010. Coordinated responses to honey bee decline in the USA. Adipologie 41:256-263.

    2.     van Engelsdorp, D., and M.D. Meixner. 2010. A historical review of managed honey bee populations in Europe and the United Sates and the factors that may affect them. Journal of Invertebrate Pathology 103:80-95.    

    3.     James, R., and T.L. Pitts-Singer. 2008. Bee Pollination in Agricultural Ecosystems. Oxford University Press, USA.

    4.     Zayed, A., and L. Packer. 2005. Complementary sex determination substantially increases extinction proneness of haplodiploid populations. Proceedings of the National Academy of Sciences of the United States of America 102:10742-10746.

    5.     Goulson, D., and K. Sparrow. 2009. Evidence for competition between honey bees and bumble bees: Effects on bumble bee worker size. Journal of Insect Conservation 13:177-181.

    6.     Thomson, D. 2004. Competitive interactions between the invasive European honey bee and native bumble bees. Ecology 85:458-470.

    7.     Goulson, D. 2003. Effects of introduced bees on native ecosystems. Annual Review of Ecology, Evolution, and Systematics 34:1-26.

    8.     Colla, S.R. 2016. Status, threats and conservation recommendations for wild bumble bees (Bombus spp.) in Ontario, Canada: a review for policymakers and practitioners. Natural Areas Journal 36:412-426.

Image Sources:

  1. https://bringbackthebees.ca

  2. https://inaturalist.com

  3. http://beeaware.org.au/archive-pest/small-hive-beetle/#ad-image-0

Tea Time with Amazigh People

Guest post by University of Toronto-Scarborough MEnvSc Candidate Erin Jankovich

 “How do they survive?” This is the question I kept asking myself over and over as I sat sipping my mint tea on the clay floor of an Amazigh cave in the Moroccan mountains. Their faces, hands, tea-kettle and even my cup were layered with dirt and soot. Outside, prevailing winds dusted the lonely peaks of the High Atlas with orange silt. I never expected to stumble across an indigenous settlement when I set out on my hike that day, let alone be invited for tea. This was by no means a fancy tea party, but it certainly was a memorable one.

Women plucked leaves from dry aromatic plants and a man filled a kettle for more tea. A toddler sat beside me and gestured to trade his clay ball for my Nikon. I felt like a fly on the wall in a National Geographic documentary.

I was on to my third cup of tea when a young man broke the silence. “Hello, do you speak English”, I heard from behind me. Dressed in traditional Amazigh clothes, this young man carrying a notepad and pen excitedly sat down beside me. He was a university student from Japan who had been living with this Amazigh family for four months to learn about their culture. Perfect! Maybe he could enlighten me as to how these people sustain their lives on this rugged mountain top - surely there was more to it than mint tea.

Mint tea, a traditional Moroccan drink and symbol of hospitality. Photography: Erin Jankovich

The young man pointed out across the valley and said “see”. For a while, all I saw was an expanse of orange rock but eventually like a stereogram the landscape came to life. Those little black dots were goats, dozens of goats! He walked me to the trailhead and pointed at the pale green tufts across the landscape. Mint, rosemary, sage, thyme, and verbena – these aromatic plants were right beneath my nose. This dusty landscape wasn’t so dead after all. He explained that the Amazigh people have extensive knowledge of the medicinal properties of hundreds of plants that grow in the High Atlas, and women will take several hour journeys to sell herbs in the valley markets. I wanted to learn more, but I was reminded of the long trek back to Tinerhir. I said goodbye, and thanked them all for such generous hospitality.

Afternoon tea with Amazigh family. Photography: Erin Jankovich

Morocco is dominated by a mountainous interior, bordered with rich coastal plains to the west and Sahara desert to the east. Since coming home from my trip, I have learned that this unique geography falls within the Mediterranean basin, a global biodiversity hotspot teeming with endemic flora and fauna found nowhere else on the planet (Rankou et al. 2013). Morocco alone has 879 endemic plants, the majority of which are restricted to the High Atlas region (Rankou et al., 2013).

The rich biodiversity of the High Atlas has been known to the Amazigh people for thousands of years, but only recently have researchers and scientists begun to draw their attention to this unique area. In 2015, scientists used IUCN Red List criteria to assess the status of endemic Moroccan flora and determined that many species are at risk of extinction due to climate change and habitat degradation (Rankou et al., 2015). These scientists emphasized that mountainous regions such as the High Atlas are especially sensitive to changes in climate and should be a top priority for conservationists, but so far very little research has gone into understanding the vegetation dynamics of this region.

Fresh and dry plants used for medicinal purposes found in traditional markets (image from Bouiamrine, 2017).

Many plant species picked by the Amazigh are highly toxic and dangerous to humans if not used appropriately (Mouhajir et al., 2001). Anecdotal evidence through surveys and interviews have revealed that the Amazigh people, specifically senior women, are experts in distinguishing between medicinal herbs and continue to pass on this traditional knowledge from one generation to the next (Bouiamrine, 2017). Many Moroccans still rely on traditional medicine to maintain good health thus conservation of these endemic herbs is critical for both the lives of the Amazigh and Moroccan market economy (Bouiamrine, 2017).

An Amazigh woman journeys across rugged terrain to sell herbs in modern markets. Photography: Erin Jankovich

I know better now that not all hotspots of biodiversity look like lush tropical jungles, but what they do have in common is an abundance of unique species that are threatened with extinction. Internationally the Mediterranean Basin has been recognized as providing significant ecosystem function and I was pleased to find that the Moroccan government has set national targets to preserve biodiversity and inventory traditional knowledge by 2020 (CBD, 2011).

Who better than the indigenous people of the High Atlas to help us understand the historical distribution of endemic plants and potential range shifts induced by climate change? Through sensitive and purposeful strategies for interaction with the Amazigh people—like the young student sharing a tea in the mountain—we may find that complimenting science with traditional ecological knowledge is the key to saving these unique landscapes.

References
Bouiamrine, E.H., Bachiri, L., Ibijbijen, J., & Nassiri, L. (2017). Use of medicinal plants in Middle Atlas of Morocco: potential health risks and indigenous knowledge in a Berber community. Journal of Medicinal Plant Studies, 5(2), 388-342.
Convention on Biological Diversity (2011). Electronic source. Retrieved from: https://www.cbd.int/countries/targets/?country=ma
Mouhajir, F., Hudson, J.B., Rejdali, M., & Towers, G.H.N. (2001). Multiple antiviral of endemic medicinal plants used by Berber peoples of Morocco. Pharmaceutical Biology, 39(5), 364-374.
Rankou, H., Culham, A., Jury, S.L., & Christenhusz M.J.M. (2013). The endemic flora of Morocco. Phytotaxa, 78 (1), 1-69.
Rankou, H., Culham, A. ,Taleb, M.S., Ouhammou, A., Martin, G., & Jury, S.L. (2015). Conservation assessments and Red Listing of the endemic Moroccan flora (monocotyledons). Botanical Journal of the Linnean Society, 177, 507-575.

Moving on up to the regional scale

Like the blind men and the elephant, perspective drives understanding in ecology. The temporal and spatial scale of analysis (let alone the system and species you focus on) has major implications for your conclusions. Most ecologists recognize this fact, but consider only particular systems, scales or contexts due to practical limitations (funding, reasonable experimental time frames, studentship lengths). 

Ecologists have long known that regional processes affect local communities and that local processes affect regional patterns. Entire subfields like landscape ecology, metapopulations, metacommunities, and biogeography (species area relationships) highlight these spatial dependencies. But high-profile ecological research into biodiversity and ecosystem functioning ('BEF') primarily considers only local communities. Recently though, the literature has started to fill this gap and asking what BEF relationships look like at larger spatial scales, and how well local BEF relationships predict those at larger spatial scales.

'Traditional' BEF experiments were done at relatively small spatial scales (often only a few meters^2). Positive BEF relationships were commonly observed, but often were quite saturating – that is, only a few species were necessary to optimize the function of interest. If the impact of biodiversity saturates with only a few species, it would seem that surprisingly few species are necessary to maintain functioning. True, studies that considered multiple ecosystem functions are more likely to conclude that additional diversity is required for optimal functioning (e.g. Zavaleta et al. 2010). But a simplistic evaluation of the facts that a) ecosystem functioning rapidly saturates with diversity, and b) locally, diversity may not be generally decreasing (Vellend et al. 2017), could lead to overly confident conclusions about the dangers of biodiversity loss. Research on BEF relationships, as they transition from local to larger spatial scales, is increasingly suggesting that our understanding is incomplete, and that BEF relationships can grow stronger at large spatial scales.

A number of recent papers have explored this question, and in considering the essential role of spatial scale. Predictions about how BEF relationships will change with spatial scale vary. On one hand, in most systems there are only a few dominant species and these species may disproportionately contribute to ecosystem functions, regardless of the spatial scale. On the other hand, species-area relationships tend to increase rapidly at small scales, as community composition turns over. If that is the case, then different species may make important contributions in different places. Winifree et al. (2018) contrasted these predictions for three crop species that rely on natural bee pollinators (cranberries, blueberries, and watermelons). They censused pollinators at 48 sites, over a total extent of ~3700 km^2. Though at local scales very few bee species were required to reach pollination goals, the same goals at larger spatial scales required nearly an order of magnitude more bee species. These results in particular appeared to be driven by species turnover among sites--perhaps due to underlying environmental heterogeneity.

From Winifree et al. "Cumulative number of bee species required to maintain thresholds of 25% (orange), 50% (black), and 75% (purple) of the mean observed level of pollination, at each of n sites (16). Horizontal dashed lines indicate the total number of bee species observed in each study. Error bars represent 1 SD over all possible starting sites for expanding the spatial extent. For all three crops combined, each x-axis increment represents the addition of one site per crop".

Another mechanism for increased BEF at larger scales is insurance effects. The presence of greater diversity can interact with spatial and temporal environmental variation to increase or stabilize ecosystem functioning. Greater diversity should maximize the differential responses of species to changing conditions, and so buffer variation in ecosystem functioning. Such effects, when they occur through time are temporal insurance, and when they occur via dispersal among sites, spatial insurance. Wilcox et al. (2018) considered the role of synchrony and asynchrony among populations, communities, and metacommunities to ask whether local asynchrony affected stability (see Figure below for a nice conceptual explanation). Across hundreds of plant data sets, they found that asynchrony of populations did enhance stability. However, the degree to which it affected stability varied from very weak to very important (e.g. by 1% to 300%). Maximizing species or population differences at local scales apparently can have implications for dynamics, and so potentially stability of functioning, at much larger scales.

From Wilcox et al. "Conceptual figure showing how stability and synchrony at various spatial scales within a metacommunity combine to determine the stability of ecosystem function (here, productivity). In (a), high synchrony of species within and among local communities results in low stability at the scale of the metacommunity. In (b), species remain synchronised within local communities, but the two communities exhibit asynchronous dynamics due to low population synchrony among local patches. This results in relatively high gamma stability. Lastly, in (c), species exhibit asynchronous dynamics within local communities through time, and species-level dynamics are similar across communities (i.e. high population synchrony). This results in relatively high gamma stability. Blue boxes on the right outline stability components and mechanisms, and the hierarchical level at which they operate. Adapted from Mellin et al. (2014)."

Finally, Isbell et al. (2018) describe ways in which ecosystem functioning and other contributions of nature to humanity are scale-dependent, laying out the most useful paths for future work (see figure below).

From Isbell et al. 2018.

These papers make nearly identical points worth reiterating here: 1) we have done far too little work beyond the smallest spatial scales (~3 m^2) and so lack necessary knowledge of the impacts of losing of biodiversity, and 2) policy decisions and conservation activities are occurring at much larger scales – at the scale of the park, the state, or the nation. Bridging this gap is essential if we are to make any reasonable arguments as to why ecosystem function figure into  large-scale conservation activities.

References:
Sustaining multiple ecosystem functions in grassland communities requires higher biodiversity. Erika S. Zavaleta, Jae R. Pasari, Kristin B. Hulvey, G. David Tilman. Proceedings of the National Academy of Sciences Jan 2010, 107 (4) 1443-1446; DOI: 10.1073/pnas.0906829107. 

Plant biodiversity change across scales during the Anthropocene. Vellend, Mark, et al. Annual review of plant biology 68 (2017): 563-586.

Species turnover promotes the importance of bee diversity for crop pollination at regional scales. RACHAEL WINFREE, JAMES R. REILLY, IGNASI BARTOMEUS, DANIEL P. CARIVEAU, NEAL M. WILLIAMS, JASON GIBBS. SCIENCE16 FEB 2018 : 791-793

Asynchrony among local communities stabilises ecosystem function of metacommunities. Kevin R. Wilcox, et al. Ecology Letters. Volume 20, Issue 12, Pages 1534–1545.

Isbell, Forest, et al. "Linking the influence and dependence of people on biodiversity across scales." Nature 546.7656 (2017): 65.

Of course we need to save endangered species: a response

I spend a lot of time thinking about the related topics of conservation, biodiversity, and evolution, so I was interested to see an editorial in the Washington Post on precisely those issues. The article, "We don’t need to save endangered species. Extinction is part of evolution" by Alex Pyron, presents a misrepresentative and potentially harmful position about the future of the earth's biota.

Pyron begins by stating that "Evolution loves death." Selection necessarily means the success of one variant at the expense of others, and today's living creatures are the survivors of an ongoing battle for existence. Extinction is not a modern phenomenon by any means. There have been five mass extinctions, including the glaciation of Gondwana and the impact of an asteroid that lead to the loss of the dinosaurs.

But the 6th great extinction (the Anthropocene extinction - the one we are currently living in) shares little in common with these past events. This is the only extinction that a single species (humans) are primarily responsible for, through activities from habitat conversion or degradation, land fragmentation, warming climate, ocean acidification, and human consumption of natural resources. In this context, Pyron's argument seems to be that we ought to retain an anthropocentric viewpoint of conservation as well. That is, we are simply selecting for species that can survive in our wake, and we should feel concern only for those species that we need.

"But the impulse to conserve for conservation’s sake has taken on an unthinking, unsupported, unnecessary urgency. Extinction is the engine of evolution, the mechanism by which natural selection prunes the poorly adapted and allows the hardiest to flourish. Species constantly go extinct, and every species that is alive today will one day follow suit. There is no such thing as an “endangered species,” except for all species. The only reason we should conserve biodiversity is for ourselves, to create a stable future for human beings. Yes, we have altered the environment and, in doing so, hurt other species. This seems artificial because we, unlike other life forms, use sentience and agriculture and industry. But we are a part of the biosphere just like every other creature, and our actions are just as volitional, their consequences just as natural. Conserving a species we have helped to kill off, but on which we are not directly dependent, serves to discharge our own guilt, but little else."

This is hardly an original viewpoint (hastening to the Bible's 'Then God said, “Let Us make man in Our image, according to Our likeness; let them have dominion over the fish of the sea, over the birds of the air, and over the cattle, over all the earth and over every creeping thing that creeps on the earth.'). But it is a short-sighted one. Ignoring more philosophical arguments about the intrinsic value of all species, the arguments presented are problematic and incomplete, and the potential cost could be huge.

Pyron notes that we may be over-estimating the loss of species:

"According to some studies, it’s not even clear that biodiversity is suffering. The authors of another recent National Academy of Sciences paper point out that species richness has shown no net decline among plants over 100 years across 16,000 sites examined around the world."

The study cited by Pyron here does not support the assertion that biodiversity is fine. In fact, Vellend et al (2013) show that at local scales, plant diversity (i.e., the number of plant species; species number being only way of characterizing biodiversity) has been stable. This isn't the same as saying species are not being lost at a global scale. In a follow-up piece (Vellend et al. 2016), the same author notes that at the global scale, "Nonetheless, if we take 142 and 592 as somewhere in the ballpark of extinctions that have occurred between 1600 and 2016, we get extinction rates of 0.98–4.1, 1–2 orders of magnitude higher than the background rate." Outside of plants, Pimm et al. (2014)'s comprehensive review of extinctions in birds, amphibians, and mammals show extinction rates have at least doubled since 1900. These are rates much higher than considered 'natural'. Even when no extinctions have occurred yet, populations are declining rapidly (Ceballos and Ehrlich 2014, Ceballos et al 2017).

An anthropocentric approach also requires complete understanding and control of our environment. Preventing the loss of the species we need or the ecosystems we rely on is not straightforward (as seen by the rarity with which species become 'non-endangered'). Humans are still under-informed about ecosystem services and goods, and what biotic and abiotic interactions are essential to maintain them. The existence of IPBES is a good indicator of how essential and lacking this information is. To confidently state that "Conserving a species we have helped to kill off, but on which we are not directly dependent, serves to discharge our own guilt, but little else" ignores the indirect linkages that might matter, and our lack of knowledge of them.

Further, the philosophy that humans will survive somehow, in the face of losses of biodiversity and changing planetary climate is probably mostly true for the richest members of the planet. Elsewhere, food shortage associated with climate change (eg.) and water shortages (eg.) already threaten individuals in less wealthy countries.

Ironically, Pyron suggests that all we need to make this reality is "moderation".

"The solution is simple: moderation. While we should feel no remorse about altering our environment, there is no need to clear-cut forests for McMansions on 15-acre plots of crabgrass-blanketed land. We should save whatever species and habitats can be easily rescued (once-endangered creatures such as bald eagles and peregrine falcons now flourish), refrain from polluting waterways, limit consumption of fossil fuels and rely more on low-impact renewable-energy sources....We cannot thrive without crops or pollinators, or along coastlines as sea levels rise and as storms and flooding intensify."

But the anthropocentric view of the world that he presents is the opposite of moderation. It favours only humans. In many ways it's the other extreme of the Half-Earth proposal that suggests we set aside half the planet made free of humans. Having been told we don't need to value species beyond our current needs and interests assumes that we will capably and correctly identify those needs and goals, including for time frames beyond our own myopic lifespans. This uncertainty means that a human-centric view may be just as harmful to humans as approaches that ascribe value for biodiversity more value. And humans have proven willing and capable of taking much broader and more effective actions, that accommodate both humans and other organisms. (As FDR said and did: "We have fallen heirs to the most glorious heritage a people ever received, and each one must do his part if we wish to show that the nation is worthy of its good fortune.")

It's frustrating to see this kind of description of biodiversity as though the earth is simply a plus-minus ledger of species – a few lost here, a few gained there.

A conservation baseline is meant to capture an idealized Eden is of course unreasonable. But Pyron's view looks like Hell. ("If this means fewer dazzling species, fewer unspoiled forests, less untamed wilderness, so be it. They will return in time.")

Edit (Nov. 24): the TL:DR is that 
a) I thought the author cherrypicked the ecological literature and downplayed what we know about the loss of biodiversity and the complex/negative effects of human actions; 
b) if the argument is that we should think about biodiversity over timescales of millions of years, humans don't matter anyways; 
c) if we do care about humans, utility values of biodiversity are an acceptable focus of conservation. But it would be misguided to think that we have a perfect understanding of how ecosystems work or a perfect ability to forecast our impacts. For reasons of uncertainty, sampling effects and option value argue that we preserve as much diversity as we can;
d) Non-economic utility values (aesthetic, cultural values) are a good argument for conservation too. Most of us want to leave our children a beautiful planet that is full of life. 

Positive cost-benefit analysis for conservation spending

In a time when most news about human impacts on the Earth's biodiversity seems to be negative, a new paper in Nature provides a glint of good news about our ability to change the current trend of loss. Encouraging new conservation efforts and funding may be contingent on providing evidence that such efforts will actually be effective.

The new report from Waldron et al. (2017) provides evidence for a predictable relationship between conservation spending and reduction of biodiversity loss. They focused on signatory countries of the Earth Summit's Convention on Biological Diversity and Sustainable Development Goals, and developed a pressures-and-conservation-impact’ (PACI) model to predict how biodiversity loss changed in these countries between 1996-2008. Improvements were driven by conservation spending (relativized to reflect differences in buying power between nations) and were counteracted by GDP growth and agricultural expansion. 

Using this model, the authors could predict how the conservation investments made in these nations had affected their loss of biodiversity, as compared to the scenario in which no investment had been made. Amazingly, the median loss of biodiversity per nation was 29% lower than would otherwise have been expected. Over 1996-2008, seven countries even had net biodiversity improvements: Mauritius, Seychelles, Fiji, Samoa, Tonga, Poland and Ukraine.

Fig 1. Map of biodiversity decline scores (BDS) for signatory nations.
"Colours show percentage of all global declines (total BDS) associated with each country. Pie charts show the predicted reduction in decline (in black) if spending had been I$5 million higher (for selected countries); pie size represents the square root of the BDS. Inset shows predicted versus observed BDS (log-transformed) for the continuous model".

They discuss a number of interactions among model terms that capture greater socio-economic complexity - for example, the impacts of GDP growth on biodiversity loss are lower when a country's base GDP is very low. Such large scale studies naturally face data limitations - here, they use mammal and bird Red List status changes to develop a quantitative measure of biodiversity loss. Other taxa presumably show similar trends, but we lack the data to incorporate them at this moment.

Hopefully by demonstrating this cost-benefit analysis for conservation actions, Waldron et al. (2017) encourage future 'investors' as to the payoff of spending on conservation. 

Reductions in global biodiversity loss predicted from conservation spending. Anthony Waldron, Daniel C. Miller, Dave Redding, Arne Mooers, Tyler S. Kuhn,  Nate Nibbelink, J. Timmons Roberts, Joseph A. Tobias & John L. Gittleman. Nature (2017). doi:10.1038/nature24295. 

Progress on biodiversity-ecosystem function requires looking back

Williams, L. J., et al. 2017. Spatial complementarity in tree crowns explains overyielding in species mixtures. - Nature Ecology & Evolution 1: 0063.

It seems at times that the focus on whether biodiversity has a positive relationship with ecosystem functioning has been a bit limiting. Questions about the BEF relationships are important, of course, since they support arguments for protecting biodiversity and suggests a cost of failing to do so. But as a hypothesis ('higher diversity is associated with higher functioning'), they can be rather one-dimensional. It's easy to think of situations in which other types of BEF relationships (neutral, negative) exist. So is it enough to ask if positive BEF relationships exist?

It’s nice then that there is increasingly a focus on identifying mechanisms behind BEF relationships, using both theory and empirical research. A new paper along these lines is “Spatial complementarity in tree crowns explains overyielding in species mixtures” from Laura Williams et al. (2017). "Overyielding" is the phenomenon in which greater total biomass is produced in a mixture of species compared to the expectation based on their biomass production in monoculture. Overyielding would suggest a benefit in maintaining polycultures, rather than having monocultures, and is a common response variable in BEF studies.

This study focused on the production of stem biomass in monocultures vs. polycultures of forest trees. Experimental communities of young tree species were planted with orthogonal gradients of species richness and functional richness, allowing the effects of species number and trait diversity to be disentangled. Complementarity in tree canopy structure in these communities may be an important predictor of overyielding in stem biomass. Complementarity among tree crowns (that is, the extent to which they fit together spatially without overlapping, see Fig below) should reflect the ability of a set of species to maximize the efficiency of light usage as it hits the canopy. Such variation in crown canopy shapes among species could lead to a positive effect of having multiple species present in a community. 

Example of crown complementarity.
From Williams et al. 2017.

To test this, the authors estimated crown architecture for each species using traits that reflect crown shape and size. These measures were used to predict the spatial complementarity expected with different combinations of tree species. In addition, a single integrative trait – maximum growth rate – was measured for each species. The authors hypothesized that the variation in growth rate of species in a community would be associated with variation in crown heights and so also a good predictor of overyielding.

They found that crown complementarity occurred in nearly all of the experimental polycultures and on average was 29% greater in mixtures than monocultures. Controlling for the number of species, communities with greater variation in growth rate did in fact have greater crown complementarity, as predicted. Further, higher levels of crown complementarity were strongly associated (R2~0.6) with stem biomass overyielding.

Fig 2&3 from Williams et al (2017). For experimental communities:
a) the relationship between crown complementarity and variation in growth rate.
b) the relationship between crown complementarity and stem biomass overyielding.

These results provide a clear potential mechanism for a positive effect of biodiversity (particularly trait-based variation) in similar forests. (As they state, "We posit that crown complementarity is an important mechanism that may contribute to diversity-enhanced productivity in forests"). Given the importance of the sun as a limiting resource in forests, the finding that mixing species that combining shade intolerant and shade tolerant strategies are more productive (the authors note that "growth rate aligns with shade tolerance and traits indicative of a tree’s resource strategy") is not necessarily surprising. It fits within existing forestry models and practices for mixed stands. This is a reminder that we already understand many of the basic components of positive (and neutral and negative) diversity-functioning relationships. The good news is that ecology has accumulated a large body of literature on the components of overyielding (limiting resources, niche partitioning, evolution of alternate adaptive strategies, constraints on these, the strength of competition, etc). From the literature, we can identify the strongest mechanisms of niche partitioning and identify the contexts in which these are likely to be relevant. For example, sun in forests and canopy complementarity, or water limitation in grasslands and so root complementarity might be a good focal trait. 

Archiving the genomes of all species

There is so much bad news about global biodiversity, that it is nice to hear about new undertakings and approaches. One of these is the 'Earth BioGenome Project' which proposes to sequence the genomes of the entirety of life on earth. Given that sequencing services have never been more affordable and more available to scientists, without question, though ambitious this is a feasible undertaking. Still, with perhaps 9 million eukaryotes on the planet, a rough prediction suggests it could take 10 years and several billion dollars to achieve.

The cost suggests a certain agony of choice - what is the best use of that amount of money (in the dream world where money can be freely moved between projects)? Direct application to conservation and management activities, or a catalog of diversity which may be the only way to save some of these species? 

Leonard Eisenberg's tree of life (https://www.evogeneao.com).

The pessimistic and optimistic view of BEF experiments?

The question of the value of biodiversity-ecosystem function (BEF) experiments—their results, their relevancy—has become a heated one in the literature. An extended argument over the last few years has debated the assumption that local biodiversity is in fact in decline (e.g. Vellend et al. 2013; Dornelas et al. 2014; Gonazalez et al. 2016). If biodiversity isn't disappearing from local communities, the logical conclusion would be that experiments focussed on the local impacts of biodiversity loss are less relevant.

Two papers in the Journal of Vegetation Science (Wardle 2016 and Eisenhauer et al. 2016) continue this discussion regarding the value of BEF experiments for understanding biodiversity loss in natural ecosystems. From reading both papers, it seems as though broadly speaking, the authors agree on several key points: that results from biodiversity-ecosystem functioning experiments don’t always match observations about species loss and functioning in nature, and that nature is much more complex, context-dependent, and multidimensional than typical BEF experimental systems. (The question of whether local biodiversity is declining may be more contested between them). 

Biodiversity and ecosystem experiments typically involve randomly assembled plant communities containing either the full complement of species, or subsets containing different numbers of species. Communities containing lower numbers are meant to provide information about the loss of species diversity a system. Functions (often including, but not limited to, primary productivity or biomass) are eventually measured and analysed in relation to treatment diversity. Although some striking results have come out of these types of studies (e.g. Tilman and Downing 1996), they can vary a fair amount in their findings (Cardinale et al. 2012).

David Wardle’s argument is that BEF experiments differ a good deal from natural systems: in natural systems, BEF relationships can take different forms and explain relatively little variation, and so extrapolating from existing experiments seems uninformative. In nature, changes in diversity are driven by ecological processes (invasion, extinction) and experiments involving randomly assembled communities and randomly lost species do nothing to simulate these processes. Wardle seems to feel that the popularity of typical BEF experiments has come at the cost of more realistic experimental designs. This is something of a zero-sum argument, (although in some funding climates that may be true...). But it is true that big BEF experiments tend to be costly and take time and labour, meaning that there is an impetus to publish as much as possible from each one. Given BEF experiments have changed drastically in design once already, in response to criticisms about their inability to disentangle complementarity vs. portfolio effects, it seems they are not inflexible about design though.

Eisenhauer et al. agree in principle that current experiments frequently lack a realistic design, but suggest that there are plenty of other types of studies (looking at functional diversity or phylogenetic diversity, for example, or using random loss of species) being published as well. For them too, there is value in having multiple similar experiments: this allows metaanalysis and comparison aggregation, and will help to tease apart the important mechanisms eventually. Further, realism is difficult to obtain in the absence of a baseline for a “natural, untouched, complete system” from which to remove species.

The point that Eisenhauer et al. and Wardle appear to agree on most strongly is that real systems are complex, multi-dimensional and context-dependent. Making the leap from a BEF experiment with 20 plant species to the real world is inevitably difficult. Wardle sees this is a massive limitation, Eisenhauer et al. sees it as a strength. Inconsistencies between experiments and nature are information that highlight when context matters. By having controlled experiments in which you vary context (such as by manipulating both nutrient level and species richness), you can begin to identify mechanisms.

Perhaps this is the greatest problem with past BEF work, is that there is a tendency to oversimplify the interpretation of results – to conclude that ‘loss of diversity is bad’ but with less attention to ‘why’, 'where', or 'when’. The best way to do this depends on your view of how science should progress. 

Wardle, D. A. (2016), Do experiments exploring plant diversity–ecosystem functioning relationships inform how biodiversity loss impacts natural ecosystems?. Journal of Vegetation Science, 27: 646–653. doi: 10.1111/jvs.12399

Eisenhauer, N., Barnes, A. D., Cesarz, S., Craven, D., Ferlian, O., Gottschall, F., Hines, J., Sendek, A., Siebert, J., Thakur, M. P., Türke, M. (2016), Biodiversity–ecosystem function experiments reveal the mechanisms underlying the consequences of biodiversity change in real world ecosystems. Journal of Vegetation Science. doi: 10.1111/jvs.12435

Additional References:
Vellend, Mark, et al. "Global meta-analysis reveals no net change in local-scale plant biodiversity over time." Proceedings of the National Academy of Sciences 110.48 (2013): 19456-19459.

Dornelas, Maria, et al. "Assemblage time series reveal biodiversity change but not systematic loss." Science 344.6181 (2014): 296-299.

Gonzalez, Andrew, et al. "Estimating local biodiversity change: a critique of papers claiming no net loss of local diversity." Ecology (2016).

Tilman, David, and John A. Downing. "Biodiversity and stability in grasslands." Ecosystem Management. Springer New York, 1996. 3-7.

Cardinale, Bradley J., et al. "Biodiversity loss and its impact on humanity."Nature 486.7401 (2012): 59-67.

Is there a limit to how many species can the earth hold?

Counting species (bird lists, plant guides) is as old as ecology itself. And yet surprisingly, there are still different opinions on how many species the planet holds, and even, whether there are limits on how many species it can have. If the number of species has ecological limits, the assumptions ecologists often make – that species pools are limited and knowable, dynamics can reach equilibrium, competition should usually be important – would be stronger. Things would be more predictable. 

But is the production of diversity self-limited? There isn’t consensus but two recent articles in the American Naturalist (continuing a debate at the American Society of Naturalists meeting) provide some excellent debate of this question.

The debate is whether the majority of variation in continental-scale species richness is regulated by diversity-dependent feedbacks. In these papers, Dan Rabosky and Allen Hurlburt argue that species richness has ecological limits, while Luke Harmon and Susan Harrison take the contrary position, that species richness is dynamic. First, to define some terms: here, species richness is being considered at the largest spatial scale (e.g. terrestrial plants at the continental scale) so that dispersal limitation should be comparatively unimportant (because diversity changes are mostly driven by in situ speciation).

The crux of the Rabosky & Hurlburt argument is established in the Ecological Limits Hypothesis (ELH), which states that species richness will reach a dynamic (i.e. stochastic) equilibrium, where equilibrium richness reflects density dependence in speciation and/or extinction rates. Speciation and extinction rates are ultimately limited by total resource availability for the continent. Therefore variance in richness through time and between places should be driven these ecological limits, and richness should be predictable.

From Rabosky & Hurlburt 2015 - the Ecological Limit Hypothesis.

The evidence presented for the ELH comes from phylogenies and macroevolutionary models, the fossil record, and macroecological observations. First, there are well known patterns between species richness and energy, productivity, or habitat area, and these span multiple regions and groups of species (e.g. Jetz and Fine 2012). Further, Rabosky & Hurlburt argue that geological records suggest that changes in diversity are not unbounded or exponential, but instead rise and fall, correcting toward some equilibrium. Molecular phylogenies are often evaluated by looking at speciation rates over time, and the authors suggest that these frequently show declines, where speciation declines during adaptive radiations. One prediction that arises from the ELH is that perturbations will be followed by particular responses: “negative perturbations—mass extinctions, in particular—should lead to diversity recoveries. Second, positive perturbations—increases in the resource base available to a biota—predict increases in species richness to stable but greater equilibrial levels”.

The rebuttal article from Harmon & Harrison takes a strong and contrasting view, although it focuses mostly on poking holes into Rabosky & Hurlburt’s arguments, rather than laying out a competing hypothesis. If Rabosky & Hurlburt focused on evidence over huge evolutionary scales and spatial expanses, the Harmon & Harrison response has a particular interest in the temporal and spatial scales of interest to community ecologists (local, present day) and how these seem to disagree with Rabosky & Hurlburt's hypothesis.

First, Harmon & Harrison argue that that the macroevolutionary evidence (molecular phylogenies, fossil data) is not nearly so convincing as Rabosky & Hurlburt suggest. There are important limits to its utility resulting from issues of ambiguity in interpretation and methodological limitations. In addition, for most of the patterns Rabosky & Hurlburt highlight, there are other papers concluding that the pattern was not present in their data. With reference to the lack of relationship between clade age and diversity: “A common interpretation of these results is that a lack of a relationship between age and diversity is evidence for ecological limits.... However… this pattern is far from ubiquitous in real data and is compatible with other explanations”. They also take issue with the tendency for hand-wave-y interpretations of patterns in such data, and emphasize the need for better statistical analyses and consideration of alternate models. Fossil data has obvious limitations as well (hence the field of taphonomy), including the fact that fossils are rarely classified to the species-level, which means they do not represent species richness, but rather lineage richness.

But Harmon & Harrison's real disagreement is based on their view that ecological evidence from local communities does not at all suggest ecological limits. Energy-richness correlations, although common, may have alternative explanations: the tropics may have higher diversification rates for other reasons, or niche conservation means that more species niches suited to the tropics, confounding energy-diversity relationships. Further, local communities do not regularly show a positive energy-diversity relationship. In particular, Harmon & Harrison suggest that the logic from the ELH, if followed, predicts that if species richness is ultimately tied to the availability of energy, then competition should necessarily be very important in most ecological communities. They cite a stat from the invasion of California flora in which alpha diversity has risen by more than 1000 invasive species, with only 28 native extinctions (as of 2002), suggesting that local (or even regional) communities are not full. 

To this, Rabosky & Hurlburt rejoins that invasion is about dispersal changes, and not resources. Further, they believe that large evolutionary scales are most useful as evidence for the ELH, since they are most likely to show zero sum game, rather than temporary dynamics, and since confounding factors should become minimized.

The debate left me feeling a little unsatisfied (since expecting the authors solve the problem is a bit unreasonable), in part because the authors are really arguing from different scales and approaches. And both sides are clearly right in some cases (and in others, perhaps, clearly overreaching). And of course, proving whether or not there is an ecological limit on diversity is a rather difficult thing. When Harmon and Harrison argue that the ELH, which assumes that richness approaches some equilibrium value but varies about it in a stochastic fashion, isn’t parsimonious, they’re wrong – ecological processes are innately stochastic and it hardly seem un-parsimonious to assume as much. But they’re right that this view makes testing and model fitting very difficult since having high replication and good quality data is necessary (to capture accurately a distribution, rather than single value). Given the variety of issues with data representing diversification over evolutionary time, and frequently an inability to capture extinction rates with evolutionary data, having quality, replicated tests of the ELH is difficult.

On the other hand, at local scales over ecological time, observations may be less relevant. It’s not clear how to reconcile statements about saturation (or lack thereof) of local communities with richness at continental scales. Rabosky & Hurlburt suggest that local assemblages can be dynamic in diversity as long as there is a zero sum across all communities and through time. But a connection between continental scales and local scales is innate, and understanding how diversity relates over multiple spatial scales is an area of ecological research we need to continue to develop.

Given there are no easy tests of this sort of question (though bacterial microcosm provide some interesting results), we have been forced to draw conclusions based on weak tests and weak evidence. But ecologists do this because this is a truly important question, with huge implications across ecology and evolution. Ecological and evolutionary models make assumptions that implicitly or explicitly about carrying capacity, about determinants of rates of speciation and extinction, about invasion, about why global diversity changes, and these need to be confirmed. Further, if there is a strong ecological feedback of diversity, one of the most important implications is that major perturbations such as extinctions should be followed by major recoveries. In the Anthropocene, that’s an important implication. 

References:

Species Richness at Continental Scales Is Dominated by Ecological Limits. Daniel L. Rabosky, Allen H. Hurlbert. The American Naturalist, Vol. 185, No. 5 (May 2015), pp. 572-583.

Species Diversity Is Dynamic and Unbounded at Local and Continental Scales. Luke J. Harmon, Susan Harrison. The American Naturalist, Vol. 185, No. 5 (May 2015), pp. 584-593.

#ibs2015 – Confronting uncertainty, biases and the unknown

The 2015 meeting of the International Biogeography Society just came to an end, and even for someone who wouldn’t traditionally consider themselves a ‘biogeographer’ there were many interesting topics and talks to see.

The focus of most talks was on biological patterns over space and/or time (or ‘deep time’, which is a fun phrase to throw around), and the talks emphasized how sophisticated statistical methodologies for such questions have become. The extent and complexity of approaches for making inferences from limited existing information, be it phylogenetic, distributional, or fossil and pollen records, is pretty amazing.

Such complicated inference needn't and shouldn't come at the cost of careful scientific work, and must include recognition of uncertainty and biases. The final sessions of the conference acted as an excellent (and at times provocative) reminder of this. For example, Joaquin Hortal advocated the development of ‘maps of ignorance’, which instead of showing the typical distributions of known information, highlight where information is missing and new sampling should be emphasized. Not only is information sometimes missing, but its value degrades over space and time. The value of a sample declines the further away you get from that site or the more different the spatial scale; samples over 50 years old may not represent current conditions any more. Predictions should consider or even incorporate this uncertainty.

Catherine Graham, David Nipperess, and Jon Chase all gave talks similarly emphasizing how fundamental consideration of scale and extent is. This is as true for phylogenetic community analysis (Graham, what extent or size of tree should be considered for analyses of community phylogenetics?); for rarefaction of phylogenetic diversity (Nipperess); or for measures of beta-diversity (Chase). Without this context, we are likely to be misunderstanding our results.

Finally, David Currie gave a damning critique of macroecology. Unfortunately, he said, macroecology seems to be a field where hypothesis testing is rare and conclusions are drawn based on spurious correlations with little explanatory and even less predictive ability. For example, why has the study of latitudinal gradients in richness progressed little beyond a list of possible correlates after more than 30 years of attention? Though Currie was focused on his own field, his comments were relevant to many ecological approaches. Currie expressed concerns about areas where scientific methods were being given short shift. In particular, he noted a lack of appropriate hypothesis testing and strong inference. Instead there is a tendency for studies to look for evidence in support of a hypothesis of interest, rather than attempting to falsify a hypothesis. Supporting evidence, sadly, does not actually increase the probability that a hypothesis is true, since the evidence could equally support some other, currently unconsidered, hypothesis. Further, correlations between variables of interest are at best a weak test of a hypothesis. The most important suggestions were that macroecologists and others should be testing the predictive ability of their hypotheses on new data sets: model fitting, in his opinion, is too often confused with model testing.

Could today’s oil rigs be tomorrow’s biodiversity hotspots?

*Guest post by Bryan Flood -one of several posts selected from the graduate EES3001 Scientific Literacy course at University of Toronto-Scarborough.

New research by Jeremy Claisse and colleagues at Occidental College in Los Angles have discovered that secondary fish production at oil and gas platforms off the coast of California is up to an order of magnitude higher than other marine ecosystems. This includes reefs and estuaries, normally considered some of the most productive ecosystems on the planet.

Photo from: US Bureau of Ocean Energy Management - http://www.data.boem.gov/homepg/data_center/other/imagecate/imageview.asp?ID=292

The authors measured the total productivity at oil and gas platforms and divided by the platform’s footprint to get a per-square-metre productivity. Herein lies the secret: The authors attribute these phenomenal productivities to the large hardscape (physical surfaces of the rigs) to seafloor ratio.

Having a structure that spans the total water column creates a range of habitats for a diverse variety of species and life stages, as well as creating a complex structure with large surface area which translates directly into habitat. This habitat attracts many species including rockfish larvae, invertebrates and planktonic food resources. These form the base of the food web, subsequently attracting adult fish and other organisms.

These results have important implications for the future of the more than 7500 oil and gas platforms around the world that will need to be decommissioned at the end of their service life. Should they be dismantled, or left as artificial reefs? Should future platforms and wind turbines be designed with an afterlife as an artificial reef in mind? Could these structures one day dot the seas with aquatic metropolises?

Claisse, J., Pondella, D., Love, M., Zahn, L., Williams, C., Williams, J., & Bull, A. (2014). Oil platforms off California are among the most productive marine fish habitats globally Proceedings of the National Academy of Sciences, 111 (43), 15462-15467 DOI: 10.1073/pnas.1411477111