The “man” in mangroves: How does the Anthropocene impact biodiversity in these ecosystems?

 *This post is by Nina Adamo, a student in Marc's 'Causes and COnsequences of Diversity' class.

Mangroves are among the most biologically important forest ecosystems on Earth, found in the intertidal zone between land and sea along tropical and subtropical coasts around the world.⁷ Mangrove ecosystems provide habitat for a wide range of terrestrial as well as aquatic organisms including plants, fish, mollusks, birds, reptiles, and crustaceans, among many others.¹

Mangroves also serve as nursery habitats for various fish and crab species found in coastal regions, as mangroves provide high abundances of food and shelter for developing wildlife living in coastal regions.⁷ Since many species use mangroves as nursery grounds, fish diversity and abundance in neighbouring coastal ecosystems has been positively linked to the proximity of mangrove areas, suggesting that mangrove habitat is critical in supporting biodiversity in surrounding coastal ecosystems.⁵

Figure 1: Many species such as fish and crustaceans use mangroves as a nursery site for their young, where shelter from predators and food is abundant.⁹

Along with supporting a wide range of biodiversity along coastal ecosystems, mangroves also provide many essential ecosystem services to humans. Some of these societal benefits include natural resources such as fish and timber, coastal protection from storms, and assisting in mitigating climate change by removing carbon dioxide from the atmosphere and storing it.¹¹

Despite the critical role mangroves play in supporting coastal biodiversity and providing ecosystem services to society, mangroves have been disappearing globally at an alarming rate of 1-2% per year due to anthropogenic activities and accelerated global climate change.⁴ The main threats to these ecosystems are rising sea levels causing coastal erosion, environmental condition changes due to climate change, land-use changes, deforestation, and overexploitation of natural resources.⁴ This has led to the loss of about 50% of mangrove coverage across the globe since 1950.¹⁰

In recent years, there have been a great number of studies that have explored the impacts of anthropogenic activities and climate change on the biodiversity of vegetation, benthic meiofauna, and benthic fauna found in mangrove ecosystems.

Figure 2: A stilt mangrove tree in a mangrove forest coastal ecosystem on an island in East Kalimantan, Indonesia.⁸

In the Sundarbans, which is the world’s largest remaining natural mangrove ecosystem located on the border of Bangladesh and India, there has been a homogenization of tree species composition over the span of 28 years from the 1980s to the 2010s.¹⁰ In other words, the largest remaining mangrove ecosystem has experienced a loss in community biodiversity of mangrove plant species over time due to anthropogenic activities and the environmental impact of climate change.

The loss of biodiversity in ecosystems is a crucial issue because higher biodiversity in most ecosystems typically leads to higher ecosystem functioning, so if biodiversity is lost through stressors such as habitat loss or extreme environmental conditions such as those produced through global climate change, it could have severe impacts on the diversity of an ecosystem and hence the functioning of the ecosystem as a whole.²

The biodiversity of benthic meiofauna, which are very small invertebrates that live in the bottom of aquatic mangrove ecosystems, are also negatively impacted by anthropogenic disturbances. In a comparison study of disturbed and undisturbed mangrove areas, disturbed areas displayed a 20% loss of benthic meiofauna biodiversity compared to undisturbed mangrove areas.² Since many juvenile fish species that use mangrove ecosystems as nursery grounds rely heavily on meiofauna for food, this loss of biodiversity through anthropogenic causes could cause a reduction in ecosystem functioning not only within mangrove communities but in surrounding coastal ecosystems as well.²

A similar observation is also found with the biodiversity of benthic fauna in mangrove ecosystems in the Philippines, where protected mangrove ecosystems have significantly higher diversity and abundance of crab species than reforested mangrove ecosystems that have been disturbed by humans.¹ This suggests that environmental factors influenced by climate change and human influences in mangrove ecosystems can have a negative impact on the biodiversity of benthic fauna, one of the most dominant groups in these systems, which could impair the overall functioning of the ecosystem.¹

With the increasing loss of mangrove habitat and the biodiversity within it across the globe due to anthropogenic activities and climate change, it is essential that humans intervene with utilizing other paradigms such as the flagship species paradigm to increase mangrove conservation and policies to protect mangrove habitat,¹¹ well-researched and well-managed mangrove planting restoration,⁶ and more research on innovative manmade artificial mangroves that may help to restore these ecosystems.³

Figure 3: Locations of the various megafauna found in mangroves (locations of mangrove areas shown in green) around the globe, with the orange representing terrestrial and the blue representing aquatic megafauna. Some examples of megafauna found in mangroves (from top-left to bottom-left in a clockwise direction) include the Key deer, Manatee, Sailfin lizard, Sawfish, Three-toed sloth, Spotted deer, Bengal tiger, Otter, Green turtle, Crocodile, and the Proboscis monkey.¹¹

The focus of much of the recent research on mangrove conservation has utilized an ecosystem services approach, where the benefits that mangroves provide to humans is stressed as an incentive for conservation.¹¹ For this reason, most of the research has been focused on smaller benthic invertebrates such as crabs and shrimp, rather than larger charismatic megafauna that are found in mangroves around the world such as sloths, Bengal tigers, green turtles, and proboscis monkeys.¹¹

Conservation awareness of mangrove ecosystems could be improved by using the flagship species paradigm which uses larger charismatic species found in mangrove ecosystems in marketing campaigns that would protect the entire ecosystem in which they are found. Since charismatic megafauna have been observed in mangrove habitats across the globe, using the flagship species paradigm in conjunction with the ecosystem services paradigm could increase public awareness of the threats facing these extremely diverse and productive ecosystems.¹¹

Conserving mangrove ecosystems around the world is important as these ecosystems provide ecosystem services to human society and play a critical role in supporting biodiversity within mangrove systems and in neighbouring coastal systems. With the increasing threat of anthropogenic activities and global climate change, the conservation and protection of mangroves is essential to reduce the decline in ecosystem functioning and biodiversity in these ecologically important ecosystems that many animals and humans alike rely on in order to live productive and successful lives.

References

1.     Bandibas, M. B., & Hilomen, V. V. (2016). Crab biodiversity under different management schemes of mangrove ecosystems. Global Journal of Environmental Science and Management, 2(1), 19–30. https://doi.org/10.7508/gjesm.2016.01.003

2.     Carugati, L., Gatto, B., Rastelli, E., Lo Martire, M., Coral, C., Greco, S., & Danovaro, R. (2018). Impact of mangrove forests degradation on biodiversity and ecosystem functioning. Scientific Reports, 8(1), 1–11. https://doi.org/10.1038/s41598-018-31683-0

3.     Florida Atlantic University. (2018). Humanmade mangroves could get to the “root” of the problem for threats to coastal areas. ScienceDaily. Retrieved February 20, 2020, from https://www.sciencedaily.com/releases/2018/08/180829115627.htm

4.     Hapsari, K. A., Jennerjahn, T. C., Lukas, M. C., Karius, V., & Behling, H. (2019). Intertwined effects of climate and land use change on environmental dynamics and carbon accumulation in a mangrove-fringed coastal lagoon in Java, Indonesia. Global Change Biology. https://doi.org/10.1111/gcb.14926

5.     Henderson, C. J., Gilby, B. L., Schlacher, T. A., Connolly, R. M., Sheaves, M., Flint, N., Borland, H. P., & Olds, A. D. (2019). Contrasting effects of mangroves and armoured shorelines on fish assemblages in tropical estuarine seascapes. Ices Journal of Marine Science, 76(4), 1052–1061. https://doi.org/10.1093/icesjms/fsz007

6.     Kodikara, K. A. S., Mukherjee, N., Jayatissa, L. P., Dahdouh‐Guebas, F., & Koedam, N. (2017). Have mangrove restoration projects worked? An in-depth study in Sri Lanka. Restoration Ecology, 25(5), 705–716. https://doi.org/10.1111/rec.12492

7.     Nagelkerken, I., Blaber, S. J. M., Bouillon, S., Green, P., Haywood, M., Kirton, L. G., Meynecke, J.-O., Pawlik, J., Penrose, H. M., Sasekumar, A., & Somerfield, P. J. (2008). The habitat function of mangroves for terrestrial and marine fauna: A review. Aquatic Botany, 89(2), 155–185. https://doi.org/10.1016/j.aquabot.2007.12.007

8.     Rante, A. (2019, December 12). A stilt mangrove tree in a protected area on Semama Island in East Kalimantan. Supertrees: Meet Indonesia’s mangrove, the tree that stores carbon. [Image].Vox. Retrieved February 20, 2020 from https://www.vox.com/2019/12/12/21009910/climate-change-indonesia-mangroves-palm-oil-shrimp-negative-emissions-blue-carbon

9.     Rante, A. (2019, December 12). In the water lapping at mangrove roots, young fish and plankton take refuge from predators. Supertrees: Meet Indonesia’s mangrove, the tree that stores carbon. [Image].Vox. Retrieved February 20, 2020 from https://www.vox.com/2019/12/12/21009910/climate-change-indonesia-mangroves-palm-oil-shrimp-negative-emissions-blue-carbon

10.  Sarker, S. K., Matthiopoulos, J., Mitchell, S. N., Ahmed, Z. U., Mamun, Md. B. A., & Reeve, R. (2019). 1980s–2010s: The world’s largest mangrove ecosystem is becoming homogeneous. Biological Conservation, 236, 79–91. https://doi.org/10.1016/j.biocon.2019.05.011

11.  Thompson, B. S., & Rog, S. M. (2019). Beyond ecosystem services: Using charismatic megafauna as flagship species for mangrove forest conservation. Environmental Science & Policy, 102, 9–17. https://doi.org/10.1016/j.envsci.2019.09.009

Losing the rainforest of the sea: Coral reef decline and loss of future ecosystem benefits and services

*This is a guest post by Karuna Sehgal - student in my 'Causes & Consequences of Biodiversity' course. 

The past three decades of human activity has altered the earth in more ways than one. The Earth is losing species, ecosystems and biodiversity because of warming climates, among other factors. Coral reefs, in particular, are greatly impacted by the rise of global surface temperatures.

Coral Reefs throughout tropical and sub-tropical oceans are under tremendous heat stress resulting in coral bleaching and mortality. Corals are animals that live in a symbiotic relationship with microscopic dinoflagellate algae that inhabit the coral tissues (Baker et al., 2008). Increased water temperatures result in corals expelling dinoflagellates living in their tissues, causing the coral to turn white, ending its symbiotic relationship (Heron et al., 2017). This does not necessarily mean death for the coral; however bleaching still adversely impacts corals by inhibiting growth and reproduction (Heron et al., 2017). This symbiotic relationship provides the coral with about 90% of the energy it needs to thrive, it also enables corals to construct limestone skeletons that form the three-dimensional structure of reefs, which provides habitat for over a million species (Heron et al., 2017. They are referred to as the Rainforests of the Sea because they are the most bio-diverse ecosystem in the ocean, comparable to rainforests on land. Species richness and the diversity found in these systems are phenomenal and breathtaking, and yet they are dying at an alarming rate.

Fig. 1: Examples of a healthy and a bleached coral reef (images modified from Wikipedia pages on coral reefs and reef degradation, respectively)

Coral Reefs provide a lot of ecological and economically important services; they gross an estimated value of over $1 trillion (USD) globally, because of their social, economic and cultural services (Heron et al., 2017). With that being said, reefs only account for less than 0.1% of the ocean floor, but host more than one-quarter of all marine fish species (Heron et al., 2017). Climate change alters the pristine attractiveness of coral reefs to tourists, which directly affects low-income coastal countries and small developing islands within coral reef regions (Hoegh-Guldberg et al., 2007). Developing countries are not equipped to respond to climate change, and many rely on tourism for the majority of their economies (Hoegh-Guldberg et al., 2007). But tourist visits are one form of valuation, coral reefs are also critical for supporting fisheries and protecting shorelines from erosion,  For the loss of reef ecosystem services it is going to cost the US about $500 billion per year by 2100 (Hoegh-Guldberg et al., 2015).

This loss of economic value through bleaching is ultimately caused by our activities. Anthropogenic activity has resulted in rising temperatures and increases in the atmospheric concentration of carbon dioxide; this has been the largest increase in global temperature since the pre-industrial times (Stocker et al., 2013). Widespread mass coral bleaching was first documented in 1983 at the time of an extremely strong El Nino (Cofroth et al., 1989). It is important to note that coral reefs have been around a long time and residing in oceans since at least the Triassic period over 200 million years ago, and are well adapted to specific environmental conditions and human activity has damaged them in a matter of 30 years. Therefore water temperatures of even 1-2^oC above the normal temperature would result in severe coral bleaching (Heron et al., 2017). It was estimated that coral reefs would take approximately 15- 25 years to recover from mass mortality, but if the frequency of mass mortality events increases to a point where the return time of mortality event is less than the time it takes to recover, the abundance of corals on reefs will decline (Heron et al., 2017).

Ocean acidification is another factor affecting coral reefs because it hinders the coral's ability to build their limestone skeletons and increases bio-erosion of reefs (Heron et al., 2017). With approximately 25% of the emitted CO₂ from anthropogenic sources entering the ocean and producing carbonic acid, which then dissociates to form bicarbonate ions and protons, reducing the availability of carbonate to biological systems (Hoegh-Guldberg et al., 2007). These high CO₂ levels and ocean acidification are expected to cause coral reefs to erode. A number of studies have determined that the doubling of pre-industrial atmospheric CO₂ to 560 ppm decreases coral calcification and growth by up to 40% through the inhibition of aragonite formation as carbonate-ion concentrations decrease (Hoegh-Guldberg et al., 2007). Studies have concluded that the corals will not thrive again until the atmospheric CO₂ has been reduced to 320-350 ppm (Heron et al., 2017).

Building the resilience of these reefs by reducing human impacts is now the main focus of organisations like the World Heritage Committee of UNESCO and the Reef Resilience Network. A World Heritage Committee analysis showed that nearly all of the 29 World Heritage coral reef sites were exposed to levels of heat stress that cause coral bleaching, more than twice per decade during the 1985-2013 period (Heron et al., 2017). Roughly 21 of the World Heritage reef properties have been exposed to repeated heat stress during the past three years (Heron et al., 2017), threatening the long-term persists of these unique and valuable places.

Fig. 2: Satellite image of coral bleaching alerts from  2014–2017 (image from NOAA Coral Reef Watch)

Bleaching and heat stress spread across tropical oceans and intensified during El Niño, and continued from La Niña and beyond (Heron et al., 2017). This period has included the three warmest years on record: 2014, 2015, and 2016 (Heron et al., 2017). Figure 2 shows that more than 70% of the global coral reef locations have experienced bleaching and most of these have experienced it twice or more, since June 2014 (Heron et al., 2017).

What is the future of these reefs? Will the next generation be able to see and explore them as we have or will they have to watch documentaries of what used to be? Coral Reefs are the most biologically diverse and economically important ecosystem on the planet, providing ecosystem services, essential to human societies and they are at danger (Hoegh-Guldberg et al., 2007).

References

Baker AC, Glynn PW, Riegl B (2008) Climate change and coral reef bleaching: An ecological assessment of long-term impacts, recovery trends and future outlook. Estuarine, Coastal and Shelf Science 80:435-471.

Cofroth MA, Lasker HR, Oliver JK (1989) Coral mortality outside of the eastern Pacific during 1982-83: Relationship to El Niño. In: Global Ecological Consequences of the 1982-83 El Niño-Southern Oscillation. Glynn, PW. (ed.). Elsevier.

Heron et al. 2017. Impacts of Climate Change on World Heritage Coral Reefs : A First Global Scientific Assessment. Paris, UNESCO World Heritage Centre.

Hoegh-Guldberg O, et al. (2015) Reviving the Ocean Economy: the case for action - 2015. WWF International, Gland, Switzerland.Geneva, 60p.

O. Hoegh-Guldberg, P. J. Mumby, A. J. Hooten, R. S. Steneck. (2007). Coral Reefs Under Rapid Climate Change and Ocean Acidificaition. Science, 318, 1-7. Doi: 10.1126/science.1152509

Stocker TF, et al. (2013) Climate Change 2013: The Physical Science Basis. Working Group 1 (WG1) Contribution to the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (AR5), Cambridge University Press. 
 

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Do the economics and logistics of field ecology bias our understanding of environmental problems?

Location of Antarctic field stations. Image from Wikipedia.

Field ecology is difficult, time-consuming and expensive. Ecologists need to make decisions about where to do research, and if research questions focus on remote locations, there are likely a lot of constraints limiting options. For example, if research requires work in the Antarctic, odds are you'll be working at one of a few locations on the coast which, depending on the nature of the research, could bias our understanding of ecological or geological processes operating there.

The research needed for some questions can literally occur almost anywhere without much worry about how local context biases findings. That's not to say that local context will not play a role in ecological dynamics, and we should always be mindful of how local conditions influence the processes we are interested in. However, some questions are sufficiently general that we could envisage running an experiment in our backyard. However, there are research questions that necessitate careful consideration of the geographical location of research.

This is especially true for questions that pertain to the consequences of environmental change on ecological systems. The drivers of environmental change, whether it be pollution, nutrient deposition, changing temperature, extreme weather events or changes in precipitation patterns, all vary across the Earth and their impacts are similarly unequal. We shouldn't expect that a 2 degree C increase in average temperature to have the same effect in the tropics as, say, the arctic.

Location of Nutrient Network sites used in Borer et al. 2014

For some research endeavors, the solution to ensuring geographical coverage has been to replicate studies around the world. Take for example studying the effects of nutrient deposition in grasslands. There is a long history of ecologists adding nitrogen, phosphorus, and other nutrients to grasslands at specific locations in short duration experiments. These studies can tell us about how plant dominance might change, but it is difficult to extend this research to other locations facing different nutrient change patterns or that are inherently structured differently. The solution to this shortcoming is best represented by the globally distributed Nutrient Network experiment. The global experiment includes dozens of sites around the world that all replicate a basic set of experimental applications of plant nutrients, which has resulted in some very influential papers about global change effects on grasslands (e.g., Adler et al. 2011, Borer et al. 2014, Seabbloom et al. 2015).

This issue of the geography of research biasing our understanding of the impacts of global change is especially true for understanding the consequences of climate change in the Arctic. This was highlighted superbly by Metcalfe and colleagues recently (Metcalfe et al. 2018). They showed that most of the terrestrial ecology research in the Arctic has occurred in just a few places. And while this work has been extremely impactful and important for understanding the ecology of Arctic systems, they are not located in places undergoing the most drastic changes in climate. Therefore, because of the geographical location of research, we might not have a very good understanding of the impacts of climate change on Arctic ecosystems.

Where research is being done in the Arctic. Panel 'a' shows where publications are coming from and 'b' shows the impact in terms of number of citations (from Metcalfe et al. 2018).

This shows where photosynthesis has changed the most, which does not correspond well to where the research has been done (from Metcalfe et al. 2018).

This type of mismatch in climate change and research requires that ecologists purposefully establish research sites in areas that are rapidly changing. Metcalfe and colleagues suggest that the governments of Arctic nations establish focused research funding to support and promote research in these regions. This of course requires government dedication. The reality is it is cheaper and more efficient to do more research in existing, well supplied, field stations. Arctic scientists and professional organizations need to lobby environment or research government departments, and this research gap is an opportunity for Arctic governments to cooperate and share research costs.

References
Adler, P. B., E. W. Seabloom, E. T. Borer, H. Hillebrand, Y. Hautier, A. Hector, W. S. Harpole, L. R. O’Halloran, J. B. Grace, T. M. Anderson, J. D. Bakker, L. A. Biederman, C. S. Brown, Y. M. Buckley, L. B. Calabrese, C.-J. Chu, E. E. Cleland, S. L. Collins, K. L. Cottingham, M. J. Crawley, E. I. Damschen, K. F. Davies, N. M. DeCrappeo, P. A. Fay, J. Firn, P. Frater, E. I. Gasarch, D. S. Gruner, N. Hagenah, J. Hille Ris Lambers, H. Humphries, V. L. Jin, A. D. Kay, K. P. Kirkman, J. A. Klein, J. M. H. Knops, K. J. La Pierre, J. G. Lambrinos, W. Li, A. S. MacDougall, R. L. McCulley, B. A. Melbourne, C. E. Mitchell, J. L. Moore, J. W. Morgan, B. Mortensen, J. L. Orrock, S. M. Prober, D. A. Pyke, A. C. Risch, M. Schuetz, M. D. Smith, C. J. Stevens, L. L. Sullivan, G. Wang, P. D. Wragg, J. P. Wright, and L. H. Yang. 2011. Productivity Is a Poor Predictor of Plant Species Richness. Science 333:1750-1753.

Borer, E. T., E. W. Seabloom, D. S. Gruner, W. S. Harpole, H. Hillebrand, E. M. Lind, P. B. Adler, J. Alberti, T. M. Anderson, J. D. Bakker, L. Biederman, D. Blumenthal, C. S. Brown, L. A. Brudvig, Y. M. Buckley, M. Cadotte, C. Chu, E. E. Cleland, M. J. Crawley, P. Daleo, E. I. Damschen, K. F. Davies, N. M. DeCrappeo, G. Du, J. Firn, Y. Hautier, R. W. Heckman, A. Hector, J. HilleRisLambers, O. Iribarne, J. A. Klein, J. M. H. Knops, K. J. La Pierre, A. D. B. Leakey, W. Li, A. S. MacDougall, R. L. McCulley, B. A. Melbourne, C. E. Mitchell, J. L. Moore, B. Mortensen, L. R. O'Halloran, J. L. Orrock, J. Pascual, S. M. Prober, D. A. Pyke, A. C. Risch, M. Schuetz, M. D. Smith, C. J. Stevens, L. L. Sullivan, R. J. Williams, P. D. Wragg, J. P. Wright, and L. H. Yang. 2014. Herbivores and nutrients control grassland plant diversity via light limitation. Nature 508:517-520.

Metcalfe, D. B., T. D. Hermans, J. Ahlstrand, M. Becker, M. Berggren, R. G. Björk, M. P. Björkman, D. Blok, N. Chaudhary, C. J. N. e. Chisholm, and evolution. 2018. Patchy field sampling biases understanding of climate change impacts across the Arctic. Nature Ecology & Evolution 2:1443.




Seabloom, E. W., E. T. Borer, Y. M. Buckley, E. E. Cleland, K. F. Davies, J. Firn, W. S. Harpole, Y. Hautier, E. M. Lind, A. S. MacDougall, J. L. Orrock, S. M. Prober, P. B. Adler, T. M. Anderson, J. D. Bakker, L. A. Biederman, D. M. Blumenthal, C. S. Brown, L. A. Brudvig, M. Cadotte, C. Chu, K. L. Cottingham, M. J. Crawley, E. I. Damschen, C. M. Dantonio, N. M. DeCrappeo, G. Du, P. A. Fay, P. Frater, D. S. Gruner, N. Hagenah, A. Hector, H. Hillebrand, K. S. Hofmockel, H. C. Humphries, V. L. Jin, A. Kay, K. P. Kirkman, J. A. Klein, J. M. H. Knops, K. J. La Pierre, L. Ladwig, J. G. Lambrinos, Q. Li, W. Li, R. Marushia, R. L. McCulley, B. A. Melbourne, C. E. Mitchell, J. L. Moore, J. Morgan, B. Mortensen, L. R. O'Halloran, D. A. Pyke, A. C. Risch, M. Sankaran, M. Schuetz, A. Simonsen, M. D. Smith, C. J. Stevens, L. Sullivan, E. Wolkovich, P. D. Wragg, J. Wright, and L. Yang. 2015. Plant species' origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands. Nat Commun 6.

#EcoSummit2016: Conferences –the piñata of ideas.

One of the greatest benefits of attending conferences is that they represent learning opportunities. I don’t necessarily mean learning about new techniques or analyses, though you can undoubtedly find out about these at conferences, but rather conferences are opportunities to hear about new concepts, ideas and paradigms. In some ways conferences are like a piñata of ideas –they are chalk full of new ideas but you never know which you’ll pick up.

Ecosummit is not the typical conference I go to, it is much more diverse in topics of talks and disciplines of the attendees. This diversity –from policy makers, to social scientists, to ecologists, means that I am exposed to a plethora of new concepts. Here are a few nuggets that got me thinking:

• Knowledge-values-rules decision making context. Policy decisions are made at the interface of scientific knowledge, human values (what is important to people –e.g., jobs), and rules (e.g., economic laws). This seems like a nice context to think about policy, though it is not clear about how we prioritize new knowledge or alter values.

 

• Adaptation services. I work on ecosystem services (e.g., carbon storage, pollination support, water filtration, etc.), but I learned that ecosystems also provide adaptation services. These are aspects of ecosystems that will help human societies adapt to climate change (e.g., new products).

• Trees and air pollution. The naive assumption most of us make about trees in urban areas are that they improve local air quality. However, I saw a couple of talks where this may not necessarily be the case. Some species in North American (red oak, sweet gum, etc.) release volatile organic compounds. Spruce plantations may not take up nitrogen oxides, and in fact might release it. Thus we need to be careful on how we sell the benefits of urban trees.

• Transformative. This is a term I have certainly heard and used before, but in listening to a wide variety of talks, I realize it is used in different contexts to mean different things. I think it best to avoid this term.

• a-disciplinary.  I heard a guy say in a talk that he was a-disciplinary and so was not bound to the dogmas and paradigms of any discipline (I already have a hard time wrapping my head around interdisciplinary, multidisciplinary, transdisciplinary, etc.). He then presented a new paradigm and a number of prescribed well-formulated tools used to move from idea, communication, to action. I think the irony was lost on him.

From the Archives: Conservation now and then

For the rest of the summer (until ESA!), we’re going to highlight some of the older topics and posts from the EEB & Flow. The blog has been around since December 2008, and so it has covered a lot of ground: 345+ posts with topics ranging from ecological history, to research advances, to work life balance, to the silly.

The interesting thing is that posts are like an archive of the various topics and directions ecological research has taken (or at least the research interests of the various post authors). And in many ways, papers from 2009 are frankly indistinguishable in topic and approach from today.

Take, for example, these posts from 2009 about conservation and climate change:

Salamanders and climate change – impending extinctions?

Fisheries and food webs: a whole system approach to cod recovery

The sushi of tomorrow… Jellyfish rolls?

Conserve now or wait for data?

The topics wouldn’t be out of place today. Risk assessments for specific species, fisheries and other applied questions, and consideration of the agony of conservation choices. 

(Not sure what this signifies - Maybe that 5 years isn't long in the grand scheme of research?)

The (changing) ecology of snow

We are well into winter in the Northern Hemisphere--Thanksgiving holidays are just around the corner in the US--and for much of the area, this is time defined by cold, dark, and snow. So it seemed appropriate to write a post about snow.

Much of the Northern Hemisphere, the Antarctic, and alpine areas are historically snow covered for more than two months of the year. In parts of the Arctic, snow cover may last 9 months of the year.

From Marchand 2014.

Though only a few degrees different from rain, snow alters an ecosystem through its unique physical properties. It is a physical force, an ecological pressure, and an opportunity: snow alters movement, creates and destroys habitat, and places immense pressures on individuals and species. The ecological implications of snow are immense and wide-ranging.

Snow has unique physical properties that make it particularly important, compared to equivalent amounts of precipitation. It stores energy and water. It insulates the soil underneath it, buffering it from cold temperatures and slowing its eventual re-warming. Snow limits light to the plants underneath it, reducing photosynthesis, and drastically cutting primary productivity during its stay. In addition to these physical properties, the sheer weight of snow has to be considered. Plants beneath a pile of snow risk compression, breakage, and deformation. 

A heavy blanket of snow, variable in its depth and consistency, changes the matrix and thus significantly alters movement: snow can ease dispersal, make it much more costly, or even prevent it altogether. Ease of movement in snow is in turn is tied to foraging and predation success. For example, small, lightweight vertebrates such as shrews become active underneath the snow, tunnelling in search of food and constructing nests under deep cover. For them, snow cover may aid winter survival. On top of the snow, some animals (hares, fox, etc.) enjoy ease of movement. If individuals are light enough to travel over the top of the snow, snow can reduce landscape complexity, burying brambles and filling hollows. However, for larger species, snow may come at a cost. Moose or reindeer for example, with their large masses and long, slender legs are at risk when snow depths are too high or a hard crust covers the snow. In these conditions, they may sink, slowing their escape from lighter predators.

Snow is difficult for all life, but plants in particular cannot escape. Places with long winter seasons and late snow melt filter out all but the most adapted vegetation. The plants common to Arctic and alpine areas share many life-history traits. Similar groups of species - mosses, lichens, low-growing shrubs, and grasses - are found in all of these areas. Such species have developed strategies for the conditions, such as seed germination cued by freeze/thaw cycles, small leaf areas to reduce water loss. There are also opportunities. Snow insulates – plants may benefit from burial under drifts, or from collecting snow in dead tissue above ground. Adaptations may permit early growth under thinning snow in the spring, by allowing photosynthesis in cold conditions and low light. 

The type, amount and depth of snow-cover may differentiate plant communities on a fine scale, between wind-exposed ridges where drought tolerance is necessary, and snow-accumulating depressions where tolerance of short growing seasons is required. Early naturalist literature recognized these snow-driven micro-differences, describing them as “schneetälchen” or little snow valleys. The Front Range of Colorado has been used for a number of studies of snow gradients on vegetation, and while many environmental factors vary along snow-melt gradients, the timing of snow melt alone greatly affects species presence and abundance.

Diagram of micro-habitats in alpine areas in Colorado,
where snow affects vegetation dynamics.

Distribution of 2 species in relation to snow depth. Both from Walker et al (2001)

Snow can be a significant source of water, sometimes the majority of water necessary for the year. It is also a sink for nutrients (N, S) from the atmosphere, the canopy, and the soil – leading it to sometimes be called ‘poor man’s fertilizer’. This isn’t always for the best – high concentrations of N and S in snowmelt can damage plant tissues, and snowdrifts can be reservoirs for airborne pollutants. In samples from the Athabasca River (Alberta, Canada), upstream of oil sands facilities, dissolved polycyclic aromatic compound levels averaged between 0.025-0.03 ug/L. However, measures from melting snow around the river had concentrations up to 4.8 ug/L, suggesting that spring snowmelt could have large environmental impacts. 

Snow algae (most common species: Chlamydomonas nivalis)
growth colours snow various shades of pink or red.

These nutrients in snow support unique microbial life. Snow algae, bacteria, yeasts and snow fungi arise. Snow algae are adapted to a life history spent wholly within melting snow – these algae find homes in glaciers, alpine peaks, and the dry valley lakes of Antarctica. These species have various adaptations to a snow-bound life, including enzymes resistant to freezing, and special pigments. These unique populations help replace some of the lost winter primary productivity. Small invertebrates graze on snow microbes, and the energy flows into local food webs.

So snow is unique, with wide-ranging implications for ecology and evolution where it occurs. But now snow is changing. Warming temperatures are having widespread and disastrous effects on snow ecosystems around the world. Arctic and alpine systems are among the most vulnerable regions to climate change, and the effects are already showing. Changes in the snow cover, depth and the timing of snowmelt are altering plant phenology and fitness, and restructuring local communities. The effects of changes in snow may be incredibly complex, may interact or be independent from changes in temperatures, and thus are difficult to predict. Some effects of changes in snow (and ice) are already obvious – for example, Glacier National Park in the US is likely to be glacier-less in 30 years. Polar bears, so reliant on their frozen habitat, face a very difficult future. But other effects are very subtle, and may take years to be fully recognized. For example, changes in snow conditions may decrease dispersal and gene flow between Canada lynx (Lynx Canadensis) populations which occur at different ends of a winter climate gradient. With declines in gene flow, the lynx may separate into two increasingly (ecologically?) distinct groups. Shrub encroachment in the low Arctic is a prime example of the complexity of changes in snow. Data shows that shrubs are increasing in abundance in the Arctic over the last 50 years. The snow-shrub hypothesis suggests that this is - indirectly - an outcome of increased snowfall in these regions (though note that warming temperatures are also causing this snow to melt earlier). Shrubs in the region accumulate larger amounts of snow in their branches, resulting in greater insulation and warmer soil temperatures. These warming temperatures encourage greater microbial activity, and perhaps enhance mineralization. The species most able to take advantage of these altered soils are, in fact, more shrubs. All of these examples are reminders that snow - and the organisms adapted to places full of snow - is changing.

References:

Ernakovich, J. G., Hopping, K. A., Berdanier, A. B., Simpson, R. T., Kachergis, E. J., Steltzer, H. and Wallenstein, M. D. (2014). Predicted responses of arctic and alpine ecosystems to altered seasonality under climate change. Global Change Biology, 20: 3256–3269. doi: 10.1111/gcb.12568

Jones, H.G. and Pomeroy, J.W. The ecology of snow-covered systems: summary and relevance to Wolf Creek, Yukon. In Wolf Creek Research Basin: Hydrology, Ecology, Environment (1999), pp. 1-15.

Kelly, E.N. , et al. (2009) Oil sands development contributes polycyclic aromatic compounds to the Athabasca River and its tributaries. PNAS, 106 (52) 22346-2235.

Larose, C., Aurélien Dommergue, and Timothy M. Vogel. (2013). The Dynamic Arctic Snow Pack: An Unexplored Environment for Microbial Diversity and Activity. Biology, 2(1), 317-330.

Marchand, P.J. (2014). Life in the Cold: An Introduction to Winter Ecology, fourth edition. University Press of New England.

Parmesan, C. (2006) Ecological and Evolutionary Responses to Recent Climate Change. Annual Review of Ecology, Evolution, and Systematics, Vol. 37, pp. 637-669

Pomeroy, J. W., and Eric Brun. "Physical properties of snow." Snow ecology(2001): 45-126.

Row, J.R., et al. (2014). The subtle role of climate change on population genetic structure in Canada lynx. Global Change Biology, doi: 10.1111/gcb.12526.

Sturm, Matthew, et al. "Snow-shrub interactions in Arctic tundra: a hypothesis with climatic implications." Journal of Climate 14.3 (2001): 336-34

Walker, D. A., W. D. Billings, and J. G. De Molenaar. (2001) "Snow–vegetation interactions in tundra environments." Snow ecology: an interdisciplinary examination of snow-covered ecosystems  266-324.

http://www.nytimes.com/2014/11/23/us/climate-change-threatens-to-strip-the-identity-of-glacier-national-park.html