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.

Frank the Fish made me an Environmental Scientist

Guest post by Neda Ejbari, MEnvSc

Children are intelligent, autonomous human beings, and although they lack experience in many things, that does not make their thoughts, feelings, and values invalid. Children are some of the most compassionate people you will meet and influencing them in a positive way early on in their development is crucial for the sake of a brighter future for humankind.

A lot of this positive influence must come from science. Understanding our planet’s functions and learning the structure and behavior of the physical and natural world is crucial to ensure that we can protect it. However, to do this, we as scientists need to be experts at communicating science. We need to pass down what we learn in a way that is understandable, not just for new-coming scientists, but for those without the background as well.

Science communication can be discouraging for many. The fear of “dumbing down” one’s work until it is no longer factual or legitimate is always a concern among scientists. In addition to this, many scientists simply do not have the background to effectively communicate their science. They might lack the training or the resources to do so. Just having the public’s attention long enough to get one’s point across can be extremely difficult to do. If someone told you there was going to be a talk about eutrophication in the Great Lakes, would you go? If you were scrolling down Twitter or Facebook, would you stop long enough to understand what that table or graph you were seeing meant?

Let’s do a little experiment. 

What graph is easier to understand?

Taken from Twitter to discuss climate change, a graph obtained from John O'Sullivan & Norm Kalmanovich’s news article: What Michael Mann’s ‘Hockey Stick’ Graph Gave To UN Climate Fraud, which was taken from Michael Mann’s 1999 paper showed a confusing analysis that is hard to interpret without some background knowledge in climate change.

Also taken from Twitter, an easy to understand tweet from Peter Gleick about climate change and what it means.

The issue with science communication is that it's a double-edged sword. You need to make your information enticing to the audience, but you need the resources and the proper training in order to do so. And the only way to get that support is through the interest and push from the public. It’s a vicious cycle; like a student being told they need experience for a job —but needing that job for the experience. The fact of the matter is; most scientists don’t have those resources or training to communicate their research to a wide audience, which makes it difficult to get the public to care for their cause and push for better science communication in the first place.

Now imagine taking that fear and doubling it as you try to communicate to children, the future of our planet’s well-being.

In a study completed by Andrea Bou - Vinals and Silvia Prock, scientists admitted to having many fears when trying to communicate with children. In Bou-Vinals and Proc’s study, scientists were made to run a workshop and roleplay with children ages 9 to 13 with the goal of engaging them in scientific activities. The consensus of this experiment was that scientists were afraid that they were boring the children or that they wouldn’t be able to get their scientific knowledge across. On the children’s end, their interpretation of the experiment was that the scientists were there to “please children, because children are the future” and “having fun with knowledge transfer.” It shows that children are aware of their importance, and the importance of learning from scientists.

So, what can we do?

We as scientists need to understand that proper, easily comprehensible communication is key to getting people to care. Scientific literature often sounds extremely unbiased and un-opinionated. The issue with this is that most people are not trained to read scientific literature. There is jargon and difficult words that many will not understand because they will never have the context for it. To communicate effectively a scientist, there must be a compromise in the language to get your point across. Sometimes, you must sacrifice the language entirely and use other means for communication, i.e., videos, infographics or applied/interactive experiments.

We as the public also need to understand that science is important. We need to improve our scientific literacy and look for answers to questions that might strike us on a day-to-day basis. We need to encourage ourselves to take the first step and seek knowledge, and in turn, pass that behaviour on to our children as well. We must expose our children to the knowledge we have, and trust that they can understand what is being presented to them. We as the public need to support our scientists and push for their information to become easily accessible and comprehensible to us, as it is the masses that often influence the choices of policy makers.

Children are important because they are easily impressionable. I speak from personal experience when I say that the most conservation-driven choices I make today stemmed from early education and youthful experience. For example, a habit that I formed when I was young was letting the tap water run while brushing my teeth. Although turning it off seems like the obvious thing to do, it was more convenient for me to let it run until I was finished. The implications behind why this was bad to do was not apparent until I watched a commercial from Sesame Street. It made the reason behind why I should conserve water very obvious and very clear to me at a young age, and I still think about it to this day.

https://www.youtube.com/watch?v=gtcZbN0Z08c

The video still holds impact. The animation is clear, the audio is crisp, and the message is still extremely relevant. What’s interesting is that the majority of the comments on the video reflected my exact thoughts and feelings. The video stuck with me after several years and is always the first thing that comes to mind when I think about conserving water, or conserving anything, for that matter. Even now, sitting in a graduate level Conservation Biology class, when we discuss the impact of human activity on the natural world, I automatically imagine Frank the Fish stuck in his dried-up pond. 

So why was this video so hard to forget? Why did it have such a clear impact on me and several others?

As a seven-year-old living on the 6^th floor of an apartment complex, I didn’t have a backyard to begin with, and yet the message was clear. Because I had seen a natural environment before, I understood that my actions were indirectly impacting that area of nature I had once seen. And because I was able to relate it to that, I was able to empathize with the commercial and change my behaviour as a result.

This video was an effective tool of science communication. As environmental scientists, we all know that running water does not directly drain a pond in your backyard. There’s a lot of complicated architect, engineering and science that goes behind how we get our clean water from the environment; and yet the public —and children especially— needed none of those small details to understand the big picture.

It was an effective tool of science communication because it showed me, and people like me, the direct impact of my behaviour in the grand scheme of things. The video influenced me as a child and encouraged me to pursue a field of biology and environmental science as a result. And now, this video will be passed down because it has been presented and saved in a form of media that can be spread and shared with a simple click of a button.

Our goal as members of the human race should be to constantly ask the question: do I understand this? Would I be able to explain this to my children so that they can understand it? Truthfully, we won’t always be able to. But if we support our scientists and give them the tools and support they need to effectively present their work to us, and trust that our children are clever enough to understand what they are being told, great things can happen.

To learn more about the importance of science communication, check out the following links:

What is Science Communication? - The EU Guide to Science Communication

English Communication for Scientists

Science Communication Breakdown

Young Scientist Series

References

Merzagora, M., & Jenkins, T. (2013). Listening and Empowering Children in Science Communication. Jcom Journal of Science Communication, 12(3).

Mann, M. E., Bradley, R. S., & Hughes, M. K. (1999). Northern hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations. Geophysical research letters, 26(6), 759-762.

Don't forget the details! Trait ecology and generality

The search for generality is perhaps the greatest driver of modern ecology and probably also the greatest source of ecological angst. Though ecological trends frequently reflect the newest, brightest hope for generality, the search for generality (perhaps by definition) encourages us to ignored details and complexities. Maybe this means that some areas of study won't develop fully until they've fallen out of fashion. And maybe this means that the most interesting science happens when the pressure to 'save community ecology' is gone. A great example of the kind of post-hype, thoughtful approach for trait-based ecology comes from Reynolds et al. (2017) in Tree Physiology. They do a really nice job of highlighting some of the details that must inform trait-based ecology. Here, Reynolds et al. take a broad comparative approach across species, but incorporate important details that have at times been overlooked - especially the role of the environment, recognizing and measuring both constitutive and plastic traits, captures that there are multiple paths (or trait combinations) that can result in similar functioning.

The authors look at four conspecific tree species (Brachychiton spp.) with different average positions along an observed moisture gradient (CMD or climate moisture deficit). Two species occupied drier areas of Australia ('xeric species'), while the other two were found in more moderate areas ('mesic species'). The authors assumed that the different distributions of these species reflect different hydraulic niches. Were species' hydraulic niches associate meaningfully with their traits, specifically those trait associated with drought stress responses. Though these species are closely related--and so huge divergences in form and function might not be expected--the costs and benefits of drought resistance should differ among the species. In dry environments, drought resistance strategies should be more important, and may select for particular traits or sets of traits. Trait states associated with drought conditions include "reduced leaf area, enhanced stomatal control, safer or more efficient xylem, increased tissue water capacitance...and/or deeper root systems " may all be selected for. On the other hand, investment in these traits when water is not limited is often costly, reducing growth and competition. This suggests a meaningful selective regime associated with the CMD gradient and trait values might exist.

One important, but oft-overlooked aspect of trait ecology is that trait values depend on both genes and the environment. Reynold et al. incorporate this fact this by manipulating water availability between drought and control treatments. They measured both constitutive components of trait values – those driven by genetics and expressed regardless of environments – and the plastic or environment-dependent components. For instance, in the presence of prolonged drought, trees might increase root production or change leaf characteristics. In addition to manipulating water availability between treatments, the authors measured nine traits related to morphology and allocation.

From Reynolds et al. 

Given the expectation that trait values reflect the complex interaction of genetics and the environment in different species, is it possible to even make simple predictions about trait-environment relationships? The authors find that "These complex relationships illustrate that assuming that individual traits (often measured on individuals under a single set of environmental conditions) reflect drought resistance is likely to be overly simplistic and may be erroneous for many species. However, our results do suggest that generalization may be possible, provided multiple traits are measured to explore specific integrated drought strategies."

Indeed, some results are relatively predictable relationships: under well-watered control conditions, the allocation of biomass matched the expectation: xeric species had higher investment in below-ground biomass and in transport tissues than the mesic species (both characteristic of a water-conserving species).

On the other hand, leaf traits such as SLA did not show any trend related to species' assumed drought tolerance, either for constitutive or plastic trait components. Sometimes traits associated with the leaf economic spectrum such as SLA are assumed to indicate stress tolerance, but this was not the case.

By far the most interesting result was the observation that the xeric species had the highest assimilation and stomatal conductance rate and the lowest water use efficiency under well-watered conditions. Only by also examining these species under drought conditions was it possible to observe that they are highly plastic with regards to water use efficiency. In fact, they show a feast or famine approach to water usage - "where high photosynthetic rates per unit leaf area and high investment in root and stem tissue even in well-watered conditions are achieved through profligate water use during rare periods of water availability, in order to establish a root system and stem storage tissues necessary to survive long periods of water stress." Under drought conditions, these species show reduced root tissue investment; in contrast, mesic species follow expected patterns and plastically increase root tissue investment.

This paper is a reminder that the details are also fascinating and informative. As humans, we may have a simplistic understanding of the realized environment sometimes. To us perhaps all water stress is similar, but for each species in this study, the long term selective pressures may be meaningfully different - in timing, duration, and life stage. This creates the potential for complex differences between species which may best be reflected via life history strategies involving multiple traits. That may still imply some degree of generality is possible, but it is multi-dimensional.

Works cited:
Victoria A Reynolds, Leander D L Anderegg, Xingwen Loy, Janneke HilleRisLambers, Margaret M Mayfield; Unexpected drought resistance strategies in seedlings of four Brachychiton species, Tree Physiology, https://doi.org/10.1093/treephys/tpx143

Life in Plastic Ain’t so Fantastic

Guest post by Louis Vassos, MEnvSci Candidate in the Professional Masters of Environmental Science program at the University of Toronto-Scarborough

Much like the Buggles’ 1980 debut album, our material preferences are well within the age of plastic. Thanks to its light weight, durability, inertness, and low manufacturing costs, our use of plastics has increased dramatically since the mid-20^th century. From bottles and toys to car parts and electronics, there is seemingly no application beyond its reach. Despite its uses and benefits, it has come under increasing scrutiny by environmentalists in recent years. In this regard, we tend to think of larger-scale and more visible environmental impacts, such as accumulation in landfills and petrochemical use in manufacturing. There has also been a significant amount of research on plastic in marine environments, usually focused on larger debris known as macroplastics. Over the past decade, however, there has been increasing concern about a new type of plastic debris in our oceans. Though its presence was first highlighted in the 1970s, we are only just beginning to realize the impact of fragments known as microplastics. As their name would suggest, they are small pieces of plastic, typically measuring less than 5mm in diameter and sorted into two distinct classifications.

Primary microplastics are manufactured to be microscopically sized and are typically used in air blasting as a paint and rust remover, as well as in personal care products as an exfoliating scrubber. This latter use has risen sharply in cosmetics and facial cleansers since the 1980s, with plastic “microbeads” replacing natural materials such as pumice and ground almonds. Regardless of application they usually enter water bodies through drainage systems, and are easily able to pass through filtration systems at sewage treatment plants due to their small size.

Microbeads in toothpaste. Retrieved from: https://blog.nationalgeographic.org/2016/04/04/pesky-plastic-the-true-harm-of-microplastics-in-the-oceans/

Secondary microplastics arise from the breakdown of larger pieces of plastic debris on both land and in water. Larger debris will typically enter marine ecosystems directly or indirectly through careless waste disposal, often being transported through river systems. Sources of transfer include coastal tourism, extreme weather events, fishing, other marine industries, and accidental spillage during transportation. Over time, a culmination of processes such as exposure to UV radiation can reduce the debris’ structural integrity, causing brittleness, cracking, and yellowing. This in turn can lead to fragmentation through abrasion and waves, and fragments will gradually become smaller over time before reaching microplastic size (Cole et al, 2011).

As Eriksen et al (2014) have estimated, there is a minimum of 5.25 trillion plastic particles weighing 268,940 tons in the world’s oceans. Microplastics account for 92.4% of this mass, and their reach has been substantial. Because of their buoyancy and durability, they have the ability to travel long distances without degrading for years. Denser plastics (such as PVC) will sink and have the potential to reach coastal sediment (Andray, 2011). Other marine microplastics will end up trapped in ocean current systems known as gyres, the most famous grouping of which is the “Great Pacific Garbage Patch” in the North Pacific Gyre. Despite what the name would suggest, it is not an island-like mass of floating debris, but is more akin to an extensive “soup” of debris difficult to see with the naked eye. At a density of 334,271 pieces/km², microplastic mass in the area was found to be 6 times that of plankton (Moore et al, 2001). 

Potential microplastic transport pathways (From Wright et al, 2013)

Densities such as this increase potential microplastic ingestion by various marine organisms, especially filter feeders, plankton, and suspension feeders. These species may mistake debris for prey based on size or colour, or passively ingest them without being selective (Wright et al, 2013). In Farrell and Nelson’s (2013) study of mussel-eating crabs, they found that it is possible for microplastics to be transferred to individuals at a higher trophic level. The large surface area to volume ratio of microplastics makes them susceptible to water-borne pollutant contamination, and can cause toxic plastic additives such as BPA and PCB to leach into the water. This debris can also act as a dispersal vector for microbial communities, including potentially pathogenic species (Jiang et al, 2018). While the ingested debris can accumulate within individuals and be transferred up the food chain, the exact effects of this are not entirely known at this point in time (Avio et al, 2017). A recent study by Lei et al (2018), however, found that microplastics can cause oxidative stress and intestinal damage in zebrafish and nematodes, and that their toxicity is closely dependent on particle size.

Intestinal damage in zebrafish caused by exposure to 1.0 mg L^-1 of different microplastic types and sizes. Photograph A shows control (top), survival (middle), and dead after exposure (bottom) zebrafish (From Jiang et al, 2018)

Fluorescent microspheres on a crab’s gill lamella transferred from ingesting mussels, each measuring 5 micrometres in diameter (From Farrell and Nelson, 2013)

          What does the future hold for microplastics? Because their effects on both marine life and humans is relatively unknown, it is important to try and prevent them from entering and accumulating within marine environments. Properly dispose of larger plastic items to prevent them from entering waterways and breaking down into secondary microplastics, and be conscious about the presence of primary microplastics in other products. Make informed decisions when buying cosmetics, and choose ones that use natural exfoliating materials. Microbead bans have already begun to be enacted in several countries, including the UK, US, Canada and New Zealand (Pfeifer, 2018). There is also the potential for future studies on topics such as the health effects of microplastic ingestion and leached additives, debris behavior within the water column, and new standardized techniques for detection and sampling (Cole et al, 2011). It is hard to say what will happen next, but the removal of these 5.25 trillion particles from our oceans will prove to be a very difficult challenge without the development of novel extraction methods.

SOURCES

Anadrady, A.L. 2011. Microplastics in the marine environment. Marine Pollution Bulletin 62:1596 – 1605

Avio, C.G., S. Gorbi, and F. Regoli. 2017. Plastics and microplastics in oceans: from emerging pollutants to emerged threat. Environmental Research 128: 2 – 11

Cole, M., P. Lindeque, C. Halsband, and T.S. Galloway. 2011. Microplastics as contaminants in the marine environment: a review. Marine Pollution Bulletin 62:2588 – 2597

Eriksen, M., L.C.M. Lebreton, H.S. Carson, M. Thiel, C.J. Moore, J.C. Borerro. F. Galgani, P.G. Ryan, and J. Reisser. 2014. Plastic pollution in the world’s oceans: more than 5 trillion plastic pieces weighing over 250,000 tons afloat at sea. PLOS One

Farrell, P., and K. Nelson. 2013. Trophic level transfer of microplastic: Mytilus edulis (L.) to Carcinus maenas (L.). Environmental Pollution 177:1 – 3

Jiang, P., S. Zhao, L. Zhu, and L. Daoji. 2018. Microplastic-associated bacterial assemblages in the intertidal zone of the Yangtze Estuary. Science of the Total Environment 624:48 – 54

Lei, L., S. Wu, S. Lu, M. Liu, Y. Song, Z. Fu, H Shi, K. Raley-Susman, and D. He. 2018. Microplastic particles cause intestinal damage and other adverse effects in zebrafish Danio rerio and nematode Caenorhabditis elegans. Science of the Total Environment 619:1 – 8

Moore, C.J., S.L. Moore, M.K. Leecaster, and S.B. Weisberg. 2001. A comparison of plastic and plankton in the North Pacific Central Gyre. Marine Pollution Bulletin 42:1297 – 1300

Pfeifer, H. 2018. The UK now has one of the world’s toughest microbead bans. CNN. Retrieved from: https://www.cnn.com/2018/01/09/health/microbead-ban-uk-intl/index.html

Wright, S.L., R.C. Thompson, and T.S. Galloway. 2013. The physical impacts of microplastics on marine organisms: a review. Environmental Pollution 178:483 – 492

The problematic charismatics: Are loveable invasives getting a free pass?

Guest post by Will Brown, MEnvSci Candidate in the Professional Masters of Environmental Science program at the University of Toronto-Scarborough

In the world of animal conservation, charismatic wildlife - those loveable, huggable species like giant pandas or koalas - take centre stage. They’re the kinds of animals you see dominating news stories, books, and movies, with less-attractive species often falling by the wayside. The concept of charismatic species is tied closely to animal conservation and protection. And the public’s love and adoration for charismatic creatures plays an essential role in the success of conservation and awareness campaigns. As flagship species they become ambassadors and icons, rallying support and focusing the public’s attention (and money) on an environmental cause or conservation program.

Figure 1 A famous example of a charismatic species used as a flagship species for a conservation group, the World Wildlife Fund (WWF). (Source)

For many years, a societal bias for charismatics has been important for protecting and conserving rare and imperilled species. But what happens when a charismatic species, rather than requiring protection, is considered an invasive pest? And how does this affect the proper implementation of invasive species management and threat abatement?

A perfect example of a charismatic species as an invasive pest is wild horses, known as brumbies, in Australia. First introduced for farm work in 1788, there are now over 400 000 brumbies throughout the country. As an invasive this species causes erosion and damages vegetation with their hard hooves and overgrazing. They damage and foul waterholes and spread weeds through seeds carried in their dung, manes, and tails. As competitors with native species, they can force wildlife from favoured habitats and dominate food and water sources. There is a significant portion of the public, however, that see the brumby as an iconic Australian species that is  ’a unique equine and epitomizes the spirit of freedom’.

 

Figure 2 Feral horses threaten fragile ecosystems in Kosciusko National Park. (Source)

To manage the impacts of brumbies in Kosciuszko National Park, a plan was released in 2016 to reduce the number of wild horses by 90% over a 20-year period. The cull was to be carried out using humane control methods including trapping, fertility control and ground shooting rather than aerial shooting and roping. The management plan sparked angry protests and fierce opposition, despite warnings from scientists about the impacts of brumbies in the region. Even though government scientists declared that the horse population in the region severely degrade natural waterways and threaten fragile native alpine wildlife, hundreds of people protested the cull in Sydney and support groups downplayed the adverse effects brumbies have had on the environment. Lisa Caldwell of the Snowy Mountain Horse Riding Association was reported as saying ‘You've got to remember that the national park is 6,900 square kilometres…horses are not going to have a huge impact on those wetlands’ (www.abc.net.au).

Now almost 2 years on, backlash to the draft legislation has halted any form of management and a new amended management plan is in the works. It is reported that the amended plan includes less aggressive reduction of wild horses, with culling more likely to reduce the numbers to several thousand rather than just 600. To overcome Australia’s environment laws that require a more complete removal of wild horses, a ‘brumbies bill’ is being put forward to give recognition to the horses’ ‘cultural significance’, providing them with legal protection to remain in the park.

Now consider how an uncharismatic species is treated in a similar situation. The feral pig, generally perceived as dirty, disease-ridden and hated by farmers, also roams through Kosciuszko National Park and has very similar impacts on the environment. Feral pigs degrade natural areas through rooting up soils, grasslands and forest litter as they feed on native plants. They also spread a number of diseases and predate on a host of native animals including insects, frogs, snakes and small ground-nesting birds. Unlike brumbies however, their numbers are managed within in the park with almost no opposition.

 

Figure 3 Feral pigs populations are controlled in Australia with minimal public opposition. (Source)

In both cases there are two species found in the same location, negatively impacting the ecosystem in a similar way. For the uncharismatic species, management plans are carried out promptly and effectively. But for the charismatic species, it seems clear that societal bias can lead to strong resistance from the public and as a result, management efforts can be delayed or watered down.

And this pattern isn’t restricted to Australia. In Canada, introduced feral cats are the No.1 killer of birds, responsible for over 100 million bird deaths per year. Even with this information available, there is no widescale control programs for managing feral cat populations. In British Columbia, an exploding European rabbit population at the University of Victoria was responsible for extensive damage to fields, lawns and mature trees. When the university tried to implement a removal program, public outcry delayed efforts and the university ended up committing to using non-lethal methods for controlling the rabbit population. Meanwhile, less cute and fluffy invasive species such as America bullfrogs in BC have active population control programs with almost no objection from the public.

Based on these examples, it is clear there is a degree of favouritism when it comes to how invasive species are perceived and subsequently managed. With an obvious bias towards charismatic species, the power of public opinion can have significant impacts on invasive species control. This in turn has the potential to result in severe ecological consequences. Unfortunately, due to the complexity of the issue there is likely no single solution. The most impactful approach may be to increase the public’s awareness of the negative impacts of invasives with a focus on how these species may be damaging native wildlife. A more controversial approach may be to simply provide government scientists with greater decision-making power when it comes to wildlife management, especially for federally and state-owned lands. Adding to the complexity of the issue is how valuable are the cultural ecosystem services provided by charismatic invasives. Are the cultural benefits of invasive species as important as those provided by native species? This is an important question that should be addressed in evaluating the overall impacts caused by invasive species. Biases present in invasion biology are rarely discussed but the issues are clear. For the effective management of all invasive species, whether huggable or ugly, these biases should be recognised and carefully considered. 

Don't be Ranunculus... Little known plant behaviours

Guest post by Agneta Szabo, MEnvSci Candidate in the Professional Masters of Environmental Science program at the University of Toronto-Scarborough

Through the scientific study of plant behaviour, we continue to discover new ways in which plants interact with their environment in animal-like ways. Words like “listening”, “foraging”, and “parenting” may seem odd to associate with plants, and yet plants show evidence of all of these behaviours. Here are some of the many ways in which plants behave.

Listening

As it turns out, plants are listening! A study by Heidi Appel and Rex Cocroft published in 2014 describes their discovery that plants can detect their predators acoustically and ramp up their defenses as a response. Appel and Cocroft recorded the sound vibrations of caterpillars chewing on Mouse‑ear Cress leaves, and played these recorded vibrations to previously unaffected Mouse-ear Cress plants over several hours before allowing caterpillars to attack the plants. The researchers found that, compared to plants that were primed with recordings of silence, those who were primed with recordings of chewing produced much higher levels of the oils glucosinolate and anthocyanin, which are toxic to caterpillars. Furthermore, Appel and Cocroft found that the plants were able to distinguish the sound vibrations caused by chewing from recordings of wind or other insect noises.

In addition to listening for their predators, plants can also listen for water. In 2017, Monica Gagliano and her colleagues published a paper showing that the Garden Pea was able to locate water by sensing the vibrations generated by water moving inside pipes. Garden Pea seedlings were planted in pots shaped like an upside-down Y, and each arm of the pot was treated with different experimental conditions. When one arm was placed in a tray of water and the other was dry, plant roots grew towards the arm with water. Seems obvious enough. However, when one arm was placed above a tube with flowing water and the other was dry, the plant roots still grew towards the water, even though there was no moisture. When given a choice between a tray of water and the tube with flowing water, the Garden Pea seedlings chose the tray of water. This led Gagliano to hypothesize that plants may use sound vibrations to detect water at a distance, but that moisture gradients allow the plants to reach their target at close proximity.

Garden Pea water acoustics experimental set-up (Gagliano et al., 2017)

Foraging

Plant roots forage for food in a similar way to animals. In his 2011 review, James Cahill explores plant root responses to varying nutrient cues in the soil. Cahill explains that plant roots are responsive to both spatial and temporal nutrient availability. For example, when a nutrient patch is placed in the soil at a distance from the plant, there is a substantial acceleration in root growth in the following days. This growth is directed precisely towards the nutrient patch, and as the root approaches its target, the rate of growth slows as the nutrient patch is consumed. Furthermore, plants develop greater root biomass in richer nutrient patches, and they allocate more root biomass to patches with increasing nutrient levels.

Other foraging plants include the parasitic Dodder vine. This plant has no roots and lives off a host plant. In 2006, Consuelo De Moraes and her team published a study demonstrating that the Dodder plant uses scent, or volatile chemical cues, to locate and select its host plant. De Moraes experimentally planted Dodder seedlings between a Tomato and Common Wheat plant, the Tomato being its preferred host. Using a time lapse camera, De Moraes captured the circling movement of the Dodder plant as it approached both host options repeatedly, before settling on the Tomato plant 90% of the time. Through further experimentation by giving the Dodder seedlings a choice between the condensed chemical odour of the Tomato plant and a live Tomato that has been covered to prevent giving off odour, it was determined that the Dodder uses the chemical signals to select its host. Without being able to “smell” the live Tomato plant, the Dodder chose to attach to the vile containing the condensed chemical odour. 

Dodder vine attaching to a Tomato plant

(PBS, 2014: https://www-tc.pbs.org/wnet/nature/files/2014/09/Mezzanine_485.jpg)

Parenting

One of the most fascinating aspects of plant behaviour is parental care and kin recognition. Suzanne Simard’s work studying forests as a complex, interconnected organism has been featured on several popular media outlets including the TED Talk series and the Radiolab podcast. Through her research, Simard discovered that through a network of mycorrhizal fungi, adult trees were nurturing their young with a targeted exchange of nutrients such as carbon and nitrogen, as well as defense signals and hormones. Through experimental plantings of Douglas Fir seedlings that were directly related to the adult trees and unrelated Douglas Fir seedlings, she found that the “mother trees” recognized and colonized their kin with larger networks of mycorrhizal fungi, and sent more carbon to these seedlings. Furthermore, there was a reduction in root competition with the related seedlings. When injured, the adult trees sent large amounts of carbon and defense signals to their young, which increased the seedlings’ stress resistance.

Tree mycorrhizal network schematic 

(Medium, 2017: https://medium.com/ideo-colab/fungal-networks-connected-businesses-b38025ca7171)

Similar recognition of kin was observed by Susan Dudley and Amanda File in a 2007 paper. In this study, Dudley and File planted related “sibling” Sea Rocket plants together in pots, as well as unrelated “stranger” Sea Rocket plants together in pots. After several weeks, the roots were cleaned and assessed. The study found that kin groups allocated less biomass to their fine roots, while stranger groups grew larger roots in order to compete for resources. The same responses were not observed when kin and stranger groups were grown in isolated pots, which suggests that the mechanism for kin recognition was through root interactions.

Although we still don’t fully understand the mechanism by which plants process information, it is clear that the way plants interact with their environment is far more complicated than we previously thought. The concept of plants as inanimate organisms, blindly competing for resources is now outdated. Continued discoveries in plant behaviour demonstrate, once again, how little we understand about the natural environment—a humbling thought in an age when humankind thinks itself superior to our fellow species.

Bibliography

Appel, H.M. & Cocroft, R.B. (2014). Plants respond to leaf vibrations caused by insect herbivore chewing. Oecologia, (2014)175: 1257–1266.

Cahill, J.F. & McNickle, G.G. (2011). The behavioral ecology of nutrient foraging by plants. Annual Review of Ecology, Evolution, and Systematics, 2011(42): 289–311.

Dudley, S.A. & File, A.L. (2007). Kin recognition in an annual plant. Biology Letters (2007)3: 435–438.

Gagliano, M., Grimonprez, M., Depczynski, M. & Renton, M. (2017). Tuned in: plant roots use sound to locate water. Oecologia (2017)184: 151–160.

Runyon, J.B., Mescher, M.C. & De Moraes, C. (2006). Volatile chemical cues guide host location and host selection by parasitic plants. Science, 313(5795): 1964–1967.

Simard, S. (2016). Suzanne Simard: How trees talk to each other [Video file]. Retrieved from https://www.ted.com/talks/suzanne_simard_how_trees_talk_to_each_other#t-18444