From June 20th to June 22nd, the United Nations Conference on Sustainable Development, or Rio+20, will take place. Let’s hope that political short-sightedness will not put overly large constraints on things that need to be done. Indeed, need to be done. One of the key factors in matters concerning sustainable development, is biodiversity. Biodiversity matters. A lot. For all of us.
So, what do we know about the current status of global biodiversity? What does the science say? A recent review addresses these questions. Upon consideration of the present evidence, the authors identify six consensus statements:
- Diminishing biodiversity has a detrimental impact on the efficiency of ecosystems in how they capture essential resources, produce biomass and recycle, as well as decompose, essential nutrients.
- Increasing biodiversity leads to more stable ecosystems.
- The effect of biodiversity on an ecosystem is nonlinear and saturating, which means that the more biodiversity decreases, the bigger the impact on the ecosystem will be.
- Biological communities with higher diversity are more productive.
- Diversity loss across trophic levels (roughly, the different levels in the food chain) can have an even larger influence than a diversity decrease within one level.
- The traits of organisms have a substantial effect on ecosystem function, which means that the loss of a certain species can have a broad array of effects.
Next, four emerging trends are identified.
- Biodiversity loss can rival the impact of other drivers of global change (pollution, climate change,…)
- the impact of decreasing biodiversity gets worse over longer time periods and larger areas.
- To maintain a functional network of ecosystems, more diversity is required than each ecosystem requires in itself.
- To understand the ecological consequences, studies of evolutionary history are important.
Finally, after a more in-depth review of the current evidence, the authors propose some future direction for biodiversity research.
- Studies of ecosystem functions and services should be integrated.
- The scope should be expanded. Basically, we need better models and more real-world studies.
- Predictions should be improved to include larger-scale patterns and the effects of biodiversity and other environmental factors should be separated.
- A more integrated approach to valuing ecosystems in economic terms should be pursued.
- We all have to work together.
In conclusion, there is a lot of work to be done, but we may have a chance. Or, as the review states:
Without an understanding of the fundamental ecological processes that link biodiversity, ecosystem functions and services, attempts to forecast the societal consequences of diversity loss, and to meet policy objectives, are likely to fail. But with that fundamental understanding in hand, we may yet bring the modern era of biodiversity loss to a safe end for humanity.
So, how much time do we have?
Time to go to work then. But how much time is left for action? A second review takes look at how long we have before we pass the point-of-no-return. As you can imagine, it’s not possible to pinpoint an exact date. However, it doesn’t look good. It is known that ecosystems can shift from one state to another one abruptly when pushed beyond a certain threshold. Recent evidence suggests that the global biosphere can do so as well. Some proposed earlier manifestations of such global shifts are the Cambrian explosion, the Big Five mass extinctions and the end of the last ice age. All pretty big changes, no?
The authors propose that such a global shift becomes quite likely when more than half of the planet’s ecosystems have undergone so-called state-shifts. This would then trigger the remaining ones, resulting in a fast global biosphere state-shift. So, where are we now? Well, for aquatic ecosystems this is very difficult to assess, but widespread effects are a reasonable assumption. For land, a more accurate statement can be made. At least 43% of terrestrial ecosystems has undergone a transformation.
Under the assumption that the average rate of land transformation per capita remains the same, the scientists that composed the review calculated that when the population hits 8.2 billion, 50% of the ecosystems shift. This is estimated to happen around 2025. We have about a decade to change things.
In conclusion, they state:
Diminishing the range of biological surprises resulting from bottom-up (local-to-global) and top-down (global-to-local) forcings, postponing their effects and, in the optimal case, averting a planetary-scale critical transition demands global cooperation to stem current global-scale anthropogenic forcings. This will require reducing world population growth and per-capita resource use; rapidly increasing the proportion of the world’s energy budget that is supplied by sources other than fossil fuels while also becoming more efficient in using fossil fuels when they provide the only option; increasing the efficiency of existing means of food production and distribution instead of converting new areas or relying on wild species to feed people; and enhancing efforts to manage as reservoirs of biodiversity and ecosystem services, both in the terrestrial and marine realms, the parts of Earth’s surface that are not already dominated by humans. These are admittedly huge tasks, but are vital if the goal of science and society is to steer the biosphere towards conditions we desire, rather than those that are thrust upon us unwittingly.
So, yes people, biodiversity and nature matter. But we’re not helpless. We can change these negative developments. Let’s hope that the participants of Rio+20 see this too and prove my not so optimistic expectations wrong…
Barnosky, A., Hadly, E., Bascompte, J., Berlow, E., Brown, J., Fortelius, M., Getz, W., Harte, J., Hastings, A., Marquet, P., Martinez, N., Mooers, A., Roopnarine, P., Vermeij, G., Williams, J., Gillespie, R., Kitzes, J., Marshall, C., Matzke, N., Mindell, D., Revilla, E., & Smith, A. (2012). Approaching a state shift in Earth’s biosphere Nature, 486 (7401), 52-58 DOI: 10.1038/nature11018
Cardinale, B., Duffy, J., Gonzalez, A., Hooper, D., Perrings, C., Venail, P., Narwani, A., Mace, G., Tilman, D., Wardle, D., Kinzig, A., Daily, G., Loreau, M., Grace, J., Larigauderie, A., Srivastava, D., & Naeem, S. (2012). Biodiversity loss and its impact on humanity Nature, 486 (7401), 59-67 DOI: 10.1038/nature11148