When you walk through a forest, you surround yourself with carbon. Every branch, every leaf, every tendril of unseen root and every inch of trunk contains carbon pulled from the atmosphere through photosynthesis. And as long as it stays stored inside that forest foliage, it’s not contributing to the rising concentrations of carbon dioxide that cause climate change.
Unfortunately, deforestation is one of the major issues of our time. According to Global Forest Watch, a platform managed by the World Resources Institute, the tropics lost 10.1 million acres of primary forest in 2022, up from 9.3 million acres in 2021. That’s a 10% increase in primary tropical forest loss in 2022 and the equivalent of losing 11 football fields of forest per minute.
Scientists say there’s at least one, not-so-obvious way to combat this loss: don’t kill elephants, poach gorillas, or wipe out hornbills, tapirs or other large-bodied wildlife that eat fruit and disperse large seeds.
The forfeit of frugivores
We often describe tropical forests as being “emptied” due to the loss of animals, commonly because of unsustainable market or subsistence hunting. Such hunting is known to have detrimental effects on target species, broader biodiversity and the livelihoods and well-being of local communities. But an often forgotten and less appreciated adverse impact of defaunation is the lowered capacity of tropical forests to sequester and store carbon, which has implications for climate change.
In fact, in a new paper by the Wildlife Conservation Society, published in the journal PLOS Biology in August 2023, researchers reported that many of the birds and mammals targeted by illegal and commercial hunting are fruit-eaters that disperse large seeds from tree species with huge capacities for storing carbon. The loss of these large frugivores (fruit-eaters)—such as hornbills, primates and toucans—changes the composition of forests over time so that wind-dispersed or small-seeded tree species with lower wood density—and therefore lower amounts of carbon—become more prevalent.
For example, in the Neotropics (the tropical, terrestrial, ecological regions of the Caribbean, Central America and South America), the loss of large primates and tapirs, which disperse seeds from large-seeded trees with higher wood density, is predicted to lead to long-term losses in aboveground tree biomass by an average of 3 to 6%, but to as much as nearly 40%. In central Thailand, tree species dependent on seed dispersal by large-bodied frugivores account for nearly one-third of the total carbon biomass.
The replanting problem
Trying to reduce net carbon emissions by restoring tropical forests through planting seeds and seedlings often doesn’t adequately address the problem of tropical forest loss. Typically, restoration efforts involve small-seeded, largely second-growth species. Large-seeded, animal-dispersed tree species are underrepresented in seedlings acquired for restoration plantations. And once lost, returning animal populations is difficult, especially in the absence of their food sources; in turn, constraining the capacity of restored forests to store and sequester carbon.
Carbon dioxide incarnate
Another not-often-thought-about, negative climate impact from the loss of wildlife through hunting and poaching is that it affects total forest carbon storage by removing animal bodies—and their carbon storage capacity. For example, an adult forest elephant holds about 1,587 pounds of carbon (2.64 tons of CO2e, or carbon dioxide equivalent). The 11,000 elephants killed in a single national park in Gabon from 2004 to 2012 would, therefore, have meant the loss of 7,920 tons of carbon storage, equivalent to 29,040 tons of CO2e.
Fortunately, there are existing markets that value the carbon sequestration and storage capacity of forests, with REDD+ (Reduced Emissions from Deforestation and Forest Degradation) being the most developed. These primarily voluntary markets have so far largely focused on the carbon in the forest trees and on reducing emissions by avoiding deforestation and forest degradation. But since the loss of large animals degrades the carbon content of the forest—over both the short and long term—there’s a market opportunity to incorporate a carbon bonus for having intact fauna. Explicitly valuing wildlife for its role in the sequestration and storage of carbon in tropical forests and creating a market for intact faunal assemblages can potentially generate significant revenues for forest and hunting management.
It sounds to me like a winning strategy: a market is one way to pay for the multifaceted programs needed to conserve forests—including their large faunal species—while also ensuring the nutritional health and well-being of local communities in carbon-friendly ways.
The wildlife-filled wilderness
These new findings underscore how ecologically intact forests—large, unbroken swaths of trees that are free of significant human-caused damage and containing the full complement of wildlife—are extremely important. High-integrity tropical forests are estimated to remove and store around 3.6 billion tons of CO2 per year from the atmosphere.
Wild animals, who already benefit us in so many ways, have a vital role to play in maintaining the robustness of such forests. Forests that still have their full array of wildlife, at healthy population densities, sequester and store more carbon than those that have lost components of their fauna. Maintaining intact wildlife is, then, a critical element of any strategy to conserve forests for addressing climate change.
Walking through a forest is one of my favorite things to do. Although I might be surrounded by carbon, I find that traipsing through the woods always provides me with a much-needed opportunity to breathe deeply of clean and oxygenated air. I feel enveloped by life: plant and animal.
As American writer, filmmaker and conservationist Lois Crisler once wrote, “Wilderness without wildlife is just scenery.”
Here’s to finding your true places and natural habitats,