Humpback Whale | Credit: Lightleak Films, AdobeStock

Animals, Biodiversity, and Climate Change

On December 19, 2022, representatives from 188 countries adopted a new agreement on biodiversity, now known as the Kunming-Montreal Global Biodiversity Framework (GBF). The 2022 GBF aims to halt and reverse biodiversity loss by adopting four overarching global goals and 23 targets, including conserving 30% of the world’s land and 30% of the world’s oceans by 2030 – widely known as the 30×30 pledge. In 2022, the Global Rewilding Alliance (GRA) published a booklet entitled “Animating the Carbon Cycle,” reporting how animals influence carbon sequestration in the biosphere. Studies examining animals’ importance in carbon sequestration is a relatively new development. Oswald Schmitz at the Yale School of Forestry and Environmental Studies has been a leading figure in the “animation” of the carbon cycle and in identifying the critical contributions that animals bring to the sequestering of carbon and the mitigation of the impact of greenhouse gases on the earth’s climate.

In 2013, Schmitz was the lead author of a paper published in Ecosystems entitled Animating the Carbon Cycle. This is an early (the first?) academic publication explicitly addressing the importance of animals in driving carbon sequestration. Until then, most of the attention given to the role of natural systems in taking up carbon from the atmosphere focused on plants and micro-organisms (that take up carbon dioxide to synthesize proteins, carbohydrates and other carbon-based macromolecules and release oxygen).

A 2006 report by Deloitte, the Whale and Dolphin Conservation Society, and the Marine Conservation Society on financing ocean conservation discussed how whale excretions drive nutrient recycling and phytoplankton growth on the ocean surface. When whales (and large fish such as tuna, billfish and sharks) die, their bodies fall to the ocean floor, leading to long-term carbon sequestration. The role of whales and large fish in sequestering carbon has only recently been examined. Most of the attention on ocean uptake on atmospheric carbon has emphasized the vital role of phytoplankton (despite amounting to only 1% of global plant biomass, phytoplankton photosynthesis produces half the world’s oxygen) and carbon storage by mangroves, seagrasses and other ocean plants. In 2019, the International Monetary Fund proposed a strategy in which protecting whales would limit greenhouse gases and global warming. The IMF asks, “What if there were a low-tech solution to this problem [removing greenhouse gases from the atmosphere] that was effective and economical and had a successful funding model.” The IMF then describes a “no-tech” opportunity identified by marine biologists – namely, increase global whale populations to capture carbon from the atmosphere. The IMF notes that the “carbon capture potential of whales is truly startling.” Each great whale sequesters around 33 tons of carbon dioxide on average. When such a whale dies, its body falls to the ocean floor, taking 33 tons of carbon out of circulation for centuries. A mature tree, by comparison, absorbs around 48 pounds of carbon dioxide a year.

In addition, whale excreta provide essential nutrients, notably iron and nitrogen, for phytoplankton, tiny creatures on the ocean surface who remove an estimated 40% of all carbon dioxide produced. More whales (there were originally around 4-5 million whales in the oceans compared to an estimated 1.3 million today) would lead to more nutrients for phytoplankton and more carbon capture. Phytoplankton are also the base of the ocean food chain, and more phytoplankton would ultimately mean more fish.

Whale populations are a classic public good. An increase in whale numbers would help mitigate global warming and lead to more productive oceans and food for people.

Whales are not the only example of creatures that could help provide a no-tech solution to climate change. The Global Rewilding Alliance published a report in 2022 that described ten case studies where animals mitigated greenhouse gas release and global warming. For example, the wildebeest population in the Serengeti grassland numbered around a million individuals at the beginning of the 20th century, but poaching and the rinderpest virus reduced their numbers to around 300,000. As a result of this drop in numbers, large swathes of the Serengeti grasslands were left ungrazed, and the dead and dried grass fueled massive wildfires. As a result, the Serengeti switched from being a carbon sink to a carbon source. However, when a rinderpest vaccine became available in the late 1950s, the vaccine combined with anti-poaching measures led to the recovery of the vast wildebeest herds and the intensity of wildfires diminished. The Serengeti again became a carbon sink.

Another example involves the forest elephants in the Congo rainforest. Nicknamed “the gardeners of the Congo,” their feeding behavior suppresses faster-growing softwood trees and aids the survival of slower-growing high-density hardwoods. Models indicate that the presence of such forest elephants can increase above-ground plant biomass by up to 54 tonnes per hectare, with each elephant helping to capture 9,000 tonnes of carbon dioxide during an average lifetime.

Beavers are well-known landscape engineers affecting carbon storage over short and long timespans. A 2012 study in the Rocky Mountains found that the sediment upstream of beaver dams contained around 12 percent carbon by weight, most of it locked in wood that decomposes only slowly in the low-oxygen environment of a beaver dam. In contrast, sediment below the dam contained only 4 percent carbon by weight. However, the biogeochemistry of beaver dams is complicated, and beaver dams could be either carbon sinks or carbon sources. More research is needed to identify what conditions would enhance carbon storage.

Sea otters are another example of an animal with an outsized impact on carbon storage. Spiky sea urchins are one of the main prey species for sea otters. The urchins can rapidly consume entire kelp forests (seaweed), but the sea otters keep urchin populations in check. Kelp forests guarded by sea otters absorb up to twelve times more carbon than unguarded forests.

Wellbeing International seeks solutions for people, animals, and the environment. The current interest in exploring how animals can help mitigate global warming, enhance biodiversity, and protect nature’s services towards a sustainable globe is a win-win-win development!

Humpback video credit: Lightleak Films, AdobeStock

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