- Halting biodiversity loss is one of the great challenges of the 21st century, and if we want international conservation policies that work, we need to urgently re-evaluate how we think ecosystems work, argue the authors of this op-ed.
- We can do so by measuring some core processes of the many unique ecosystems, by employing factors like proxy measuments and analyzing the local ecological and environmental processes taking place in an ecosystem.
- Nations must move away from simplistic policy based on a desire for general rules and instead embrace the complexity of their ecosystems, with the help of researchers and scientists. “Only by protecting this complexity can we protect our diversity into a changing future.”
- This post is a commentary. The views expressed are those of the authors, not necessarily of Mongabay.
Halting biodiversity loss is one of the great challenges of the 21st century, but our current approaches to global conservation are clearly not working. A good example of this is the UN Convention on Biological Diversity’s (CBD) Aichi targets, an ambitious suite of twenty global conservation goals running between 2011 and 2020. Not one of these targets was met in a meaningful way. If we want an international conservation policy that works, we need to think differently about how we approach it, and a crucial starting point is to urgently re-evaluate how we think ecosystems work.
Firstly, ecosystems are incredibly complicated. They are three-dimensional tapestries of plants, animals, fungi, and micro-organisms, all interconnected and interacting with each other. These systems are then further shaped by non-living (abiotic) factors, such as climate, rainfall, geology, sunlight, and water and soil chemistry. A single ecosystem is a phenomenal web of interacting processes and relationships, so how can we devise conservation policy that will ensure its effective function into the future? And then, how can we scale this up to create policy that will protect all the at-risk ecosystems around the world?
Often, we look for globally generalizable rules about how ecosystems function or respond to disturbances, regardless of the ecosystem type or location. Once we know what these rules are, we can structure broad (i.e. global) conservation policy around them, hopefully resulting in positive impacts on global biodiversity. However, this all obviously hinges on the presumed existence of general ecological rules which are equally true for ecosystems in rainforests, tundra, deserts, or the ocean.
Do general rules exist for how ecosystems function?
This is not a new debate. In 1999 the ecologist John Lawton wrote an article entitled “Are there general laws in ecology?” Here, Lawton argued that some commonalities do exist in the natural world, but very few are universally true. Further, these laws, and particularly the mechanisms which underpin them, are always mediated by the biological processes and interactions taking place in the local environment – i.e., their ecological context. Let us look at a few examples of processes that take place in, and help to shape, ecosystems around the world.
Was Lawton right?
Firstly, if we want to understand how an ecosystem functions, we should probably start by measuring some core processes. In wooded ecosystems such as forests, the productivity of plants, or the amount of organic matter made through photosynthesis, is one such process. However, directly measuring this can be tricky, so we often rely on a proxy measure to estimate productivity. Proxy measures select a related but more accessible feature of the ecosystem to measure, and so approximate the value of the true measure we are interested in. For productivity, we often use above-ground biomass – the amount of tree or shrub matter occurring above ground in the ecosystem – as a proxy. For such a measure to be effective, it must have a stable and predictable relationship with the targeted feature we want to measure.
Perhaps unsurprisingly, given the topic of this piece, the more we dig into this proxy measure, the less reliable this relationship becomes. There is research to show that the relationship between above-ground biomass and forest productivity can indeed be stable and predictable. We now know that it can also vary greatly, and can even be the opposite of what we might expect, depending on things like the age of the plants measured, the scale at which we take measurements, and the successional stage of the forest. We are also increasingly learning that proxy measures like these are commonplace in ecosystem research, and may not always be reliable.
We find comparable patterns when we look at more recent attempts to understand how biodiversity affects ecosystem processes and functions. We assume that greater biodiversity means more stable, resilient, and functional ecosystems, and there is substantial research showing that this is true in some situations. However, there is also strong evidence this relationship is heavily influenced by the local ecological and environmental processes taking place in the ecosystem. For example, the role a species plays in an ecosystem can change depending on its life stage, or population size, or the time of the year, or the spatial scale we are interested in. Thus, differences between individuals or populations of the same species can affect how biodiversity influences ecosystem processes.
This becomes even more complicated when we look at how we define, and therefore measure, the features we are interested in. What do we mean by biodiversity, or ecosystem function, or stability? Ecosystem stability in the face of fire is very different to stability in the face of climate change, or deforestation, and all of these differences impact the relationship that we are trying to understand.
These patterns – of seemingly general rules and relationships that on closer examination turn out to be heavily influenced by local processes in the ecosystem (i.e., ecological context) – turn up again and again in ecosystem research. And yet, global biodiversity policy has for years been based on the assumptions that these rules exist and are reliable. They are clearly not. Indeed, some of the core criticisms of the failed Aichi Targets are that they relied too heavily on generalized, overly simplistic understanding of biodiversity and ecosystems. These included simple area-based protection models, or biodiversity metrics which focused on species richness over the processes and relationships between species and other entities which structure ecosystem function.
Where to from here?
We are now at a critical point for global biodiversity conservation. The COP15 conference in Montreal last year ratified the CBD’s 2020-2030 global conservation policy framework, and there are encouraging signs in the framework text. It mentions the importance of enhancing biodiversity and ecosystem functions and targeting areas of particular importance for ecosystem function for protection – both actions that will require an in-depth understanding of the processes and relationships which drive ecosystem function.
It is now up to the member nations to translate this into effective national policies by 2024, but for this to happen, we must move away from simplistic policy based on a desire for general rules. We must embrace the complexity of our ecosystems, wherever in the world we may be, and embed within our national and regional conservation plans the core ideas of ecological context.
This is achievable, but governments and policymakers will need all the help we can give them, both in research and science communication. The good news is that recent research is increasingly recognizing the importance of ecological context for understanding how biodiversity and ecosystems function. For example, a new framework for classifying all global ecosystems was published late last year.
This framework explicitly acknowledges that the properties of an ecosystem are shaped by key contextual processes, including biotic interactions, disturbance regimes, available resources, ambient environment, and human activity. It then seeks to classify ecosystems based on the ecological context which shapes them.
But there is also another potential outcome here. If similar processes create similar-functioning ecosystems, then perhaps we might uncover not globally generalizable rules, but more specialized rules that hold across similar-functioning ecosystems.
Research such as this gives us hope that we can develop new approaches which will lead to effective global policy driving real conservation outcomes. But to achieve this, we absolutely need to leave the reductionist approaches of the past behind. Lawton was right, and we cannot keep searching for inviolable rules that govern ecosystem functioning. We simply don’t have the time. Instead, we should be looking at the ecological context which structures and influences the processes, relationships and feedbacks which drive ecosystem function and identity.
Only by protecting this complexity can we protect our diversity into a changing future.
Banner image: Red poppies among other wild flowers. Image by corina ardeleanu via Unsplash (Public domain).
All authors work at The Icelandic Museum of Natural History. The lead author, Anthony Schultz, is a biodiversity research specialist. He has a background in conservation genetics and spatial ecology and is currently investigating approaches and applications of biodiversity concepts across research, policy, and education.
Small conservation areas provide large benefits for biodiversity (commentary)
Citations:
Johnson, C. N., Balmford, A., Brook, B. W., … Wilmshurst, J .M. (2017). Biodiversity losses and conservation responses in the Anthropocene. Science, 356(6335), 270-275. doi:10.1126/science.aam9317
Pörtner, H.-O., Scholes, R. J., Agard, J., Archer, E., … Ngo, H. (2021). IPBES-IPCC co-sponsored workshop report synopsis on biodiversity and climate change. Zenodo. doi:10.5281/zenodo.4782538
Díaz, S., Settele, J., Brondízio, E. S., … Zayas, C. N. (2019). IPBES: Summary for Policymakers of the IPBES Global Assessment Report on Biodiversity and Ecosystem Services. Zonodo. doi:10.5281/zenodo.3553579
Simberloff, D. & Losos, J. B. (2004). Community Ecology: Is It Time to Move On? (An American Society of Naturalists Presidential Address). The University of Chicago Press, 163, 787–799. doi: 10.1086/420777
Lawton, J. H. (1999) Are There General Laws in Ecology? Oikos, 84, 177–192. doi:10.2307/3546712
Terhorst, C. P. & Munguia, P. (2008). Measuring ecosystem function: consequences arising from variation in biomass-productivity relationships. Community Ecology, 9, 39–44. doi:10.1556/ComEc.9.2008.1.5
Keeling, H. C. & Phillips, O. L. (2007). The global relationship between forest productivity and biomass. Global Ecology and Biogeography, 16, 618–631. doi:10.1111/j.1466-8238.2007.00314.x
Stephens, P. A., Pettorelli, N., Barlow, J., Whittingham, M. J. & Cadotte, M. W. (2015). Management by proxy? The use of indices in applied ecology. Journal of Applied Ecology, 52, 1–6. doi:10.1111/1365-2664.12383
Eigenbrod, F., Armsworth, P. R., Anderson, B. J., … Gaston, K. J. (2010). The impact of proxy-based methods on mapping the distribution of ecosystem services. Journal of Applied Ecology, 47, 377–385. doi:10.1111/j.1365-2664.2010.01777.x
Blanchet, F. G., Cazelles, K. & Gravel, D. (2020). Co-occurrence is not evidence of ecological interactions. Ecology Letters, 23, 1050–1063. doi:10.1111/ele.13525
Cardinale, B. J., Matulich, K. L., Hooper, D. U., … Gonzalez, A. (2011). The functional role of producer diversity in ecosystems. American Journal of Botany, 98, 572–592. doi:10.3732/ajb.1000364
Isbell, F., Calcagno, V., Hector, A., … Loreau, M. (2011). High plant diversity is needed to maintain ecosystem services. Nature, 477, 199–202. doi:10.1038/nature10282
Tilman, D., Isbell, F. & Jane M. Cowles. (2014). Biodiversity and Ecosystem Functioning. Annual Review of Ecology, Evolution, and Systematics, 45, 471–493. doi:10.1146/annurev-ecolsys-120213-091917
Gonzalez, A., Germain, R. M., Srivastava, D. S., … Loreau, M. (2020). Scaling-up biodiversity-ecosystem functioning research. Ecology Letters, 23, 757–776. doi:10.1111/ele.13456
Srivastava, D. S. & Vellend, M. (2005). Biodiversity-Ecosystem Function Research: Is It Relevant to Conservation? Annu. Rev. Ecol. Evol. Syst., 36, 267–294. doi:10.1146/annurev.ecolsys.36.102003.152636
Thompson, P. L., Isbell, F., Loreau, M., O’Connor, M. I. & Gonzalez, A. (2018). The strength of the biodiversity–ecosystem function relationship depends on spatial scale. Proceedings of the Royal Society B: Biological Sciences, 285. doi:10.1098/rspb.2018.0038
Des Roches, S., Post, D. M., Turley, N.E., … Palkovacs, E. P. (2018). The ecological importance of intraspecific variation. Nature Ecology & Evolution, 2, 57–64. doi:s41559-017-0402-5
Violle, C., Enquist, B. J., McGill, B. J., … Messier, J. (2012). The return of the variance: intraspecific variability in community ecology. Trends in Ecology & Evolution, 27, 244–252. doi:0.1016/j.tree.2011.11.014
Ives, A. R. & Carpenter, S. R. (2007). Stability and Diversity of Ecosystems. Science, 317, 58–62. doi:10.1126/science.1133258
Pennekamp, F., Pontarp, M., Tabi, A., … Petchey, O. L. (2018). Biodiversity increases and decreases ecosystem stability. Nature, 563, 109–112. doi:s41586-018-0627-8
Secretariat of the Convention on Biological Diversity. (2020). Global Biodiversity Outlook 5. https://www.cbd.int/gbo5
Conference of the Parties to the Convention on Biological Diversity. (2022). Kunming-Montreal Global Biodiversity Framework, 14. https://www.cbd.int/doc/decisions/cop-15/cop-15-dec-04-en.pdf
Keith, D. A., Ferrer-Paris, J. R., Nicholson, E., … Kingsford, R. T. (2022). A function-based typology for Earth’s ecosystems. Nature, 610, 513–518. doi:10.1038/s41586-022-05318-4
Credits
