How ‘Animating the Carbon Cycle’ Can Help Slow Global Warming
An overlooked tool in fighting climate change is using animal biodiversity conservation to improve ecosystem carbon storage. Key to this is appreciating that rich variety of ways that animals can control the ability of ecosystems to capture and store atmospheric CO2.
By Oswald Schmitz, Yale School of the Environment
As natural wonders go, perhaps the most awe-inspiring is the annual migration of 1.2 million wildebeest flowing across East Africa’s vast Serengeti grassland. It would be a tragedy to lose these animals. But we almost did in the mid-20th century when, decimated by disease and poaching, their numbers crashed to 300,000.
The consequences of that collapse were profound. Much of the Serengeti ecosystem remained ungrazed. The accumulating dead and dried grass in turn became fuel for massive wildfires, which annually burned up to 80 percent of the area, making the Serengeti an important regional source of carbon dioxide emissions.
Then, conservation programs to eradicate disease and crack down on poaching led to the recovery of the wildebeest, restoring the grazing system and reversing the extent of the large-scale wildfires. Grazing now causes much of the carbon in grass to be released as animal dung, which is in turn incorporated by insects into soil reservoirs that are not prone to burning. The Serengeti ecosystem has now reverted to a carbon dioxide sink so large that it is estimated to offset all of East Africa’s current annual fossil fuel carbon emissions.
The wildebeest decline and recovery taught a valuable lesson, not only in how easy it is to lose an iconic animal species, but, more importantly, how the loss of a single species can have far-reaching ramifications for ecosystems — and the climate. Mounting evidence from ecological science is showing that one or a few animal species can help determine the amount of carbon that is exchanged between ecosystems and the atmosphere. It’s not that any single animal species by itself has a huge direct effect on the carbon budget. Rather, as the wildebeest case shows, by being an integral part of a larger food chain the species may trigger knock-on effects that grow through the chain to drive significant amounts of carbon into long-term storage on land or in the ocean.
Recent studies have shown, for example that the loss of important predators — from wolves in boreal forests to sharks in seagrass meadows — can lead to growing populations of terrestrial and marine herbivores, whose widespread grazing reduces the ability of ecosystems to absorb carbon. Still, the impact of biodiversity loss on the climate system is underappreciated, and reversing that loss is rarely considered as an effective tool to help slow the buildup of atmospheric carbon dioxide.
There are many more examples of animal-driven effects that hold the promise of increasing carbon storage across many different species and ecosystems. The potential magnitudes of these effects are on the same order as conventional land management activities, such as reforestation or planting new forests — policies that are increasingly being promoted as environmentally friendly alternatives to technological geoengineering.
The rub is that individual animal species tend to occur regionally, not globally. This means that we need to shy away from trying to find the single, global-scale, home run, geo-engineering solution and seek more regionally nuanced alternatives. This approach would take into account the values and preferences of local societies and would allow regional players to reconcile their particular concerns and values with broader climate solutions. The many local and regional strategies then add up globally to create a portfolio of solutions that together can meaningfully help slow climate change.
Note: This is a shortened version of a blog from 2016. Read the full version here.