Animals Shape the Earth

Wild animals are not just the inhabitants of the natural world—they are its architects. That’s the exciting finding from a new study that reveals how hundreds of species have shaped the landscapes we depend on, from beavers creating entire wetlands to hippos carving drainage systems.

A corollary study shows the other intriguing side of this hand-in-glove relationship: specific mammal traits—such as body mass and tooth shape—evolved with animals’ changing environments over time, revealing factors that caused biodiversity losses and how those absences affected the functioning of those mammal communities.

And, as specific proof of animal architects, another report demonstrates that African forest elephants play a key role in creating forests in Africa that store more atmospheric carbon than those that don’t support the presence of the elephants. If the already critically endangered forest elephants become extinct, the rain forests of Central and West Africa will lose between 6% and 9% of their ability to capture atmospheric carbon, amplifying planetary warming.

Animals as architects of the Earth

Published in the journal Proceedings of the National Academy of Sciences on February 18, 2025, a new, first-of-its-kind global synthesis led by England’s Queen Mary University of London researchers identifies 603 species, genera or families that influence Earth’s surface processes. From tiny ants shifting soil to salmon reshaping riverbeds, the study highlights the diversity and scale of animals’ impacts across all freshwater and terrestrial ecosystems.

By estimating the collective energy of these “natural engineers,” the research shows that their geomorphic contributions rival those of hundreds of thousands of major floods. Here are some more key insights from the study:

• Animal architects represent unexpected diversity: Beyond iconic examples, such as beavers and salmon, the study identifies hundreds of species—including birds, fish, insects, mammals and reptiles—that shape landscapes in remarkable ways.

• Freshwater ecosystems house many of them: Despite covering just 2.4% of the planet’s surface, freshwater habitats host over a third of these remarkable species.

• They put out an impressive amount of energy: Animals collectively contribute at least 76,000 gigajoules (a joule is a unit of energy equal to the work done by a force of one newton acting through one meter; a gigajoule is equal to one-thousand-million joules) of energy annually to shaping the Earth’s surface—a figure comparable to hundreds of thousands of extreme floods. This estimate is likely conservative, as significant knowledge gaps exist, particularly in subtropical and tropical regions where biodiversity is high, but research is limited.

• There are fascinating examples: Termites build vast networks of mounds in Brazil—some covering hundreds of square miles—while spawning salmon can shift as much sediment as annual flooding. Even ants, through their tiny but countless actions, alter drainage and soil structure.

The scientists conclude that their research shows that the role of animals in shaping Earth’s landscapes is much more significant than previously recognized. But we risk losing these crucial, diverse and natural processes as biodiversity declines. Nearly 30% of the identified species are endemic, rare or threatened, meaning vital geomorphic processes could cease before their full significance is understood. This loss could have profound consequences for landscapes and the ecosystems they support.

Extinctions as echoes of ecometrics

Not only do animals play a major role in shaping Earth, losing them remakes whole ecosystems. Another study, published in the journal Nature Communications in July 2023, shows just how the loss of species—especially large-bodied mammals—affects ecosystems.

Large-bodied mammals create habitats, help plants thrive, serve as prey and even influence how wildfires burn. But today, fewer than half of the large mammal species that were alive 50,000 years ago still exist, and those that remain are often threatened with extinction from intensifying climate change and human activities.

While many mammal extinctions are well documented, very little research has explored the impact those losses had on the nuanced ways in which mammal communities interact with their environments. So, researchers from the Georgia Institute of Technology in Atlanta developed a novel methodology to investigate how mammals’ abilities to function in their environments have been threatened in the past and what challenges they can expect to face in the future.

The scientists began by diving into a collection of data from 186 sites across East Africa. The data contained records of more than 200 extinct and 48 modern herbivore species (including the African elephant, giraffe, hippopotamus and zebra), showing where and when each species lived at a given point in time over the past 7.4 million years. The facts showed that mammal biodiversity in East Africa began to decline around 5 million years ago. They also revealed that aspects of biodiversity decline happened at multiple points, and that extinctions coincided with environmental changes and the emergence of early humans. But the scientists went further; they wondered what they’d find if they investigated how the mammals’ physical traits changed as their environments changed over time, rather than just looking at biodiversity patterns. That’s important because if a mammal species possesses traits that are well-suited to its environment, it’s better able to contribute to the functioning of that environment. But if that is not the case, environments may not function as well as they could.

To paint a fuller picture, they needed to examine biodiversity from a different perspective. This required a fresh approach, which led them to adapting a methodology known as ecometrics, a strategy that looks at the relationships between the environmental conditions where an animal lives—such as vegetation and weather—and the animal’s functional traits, those that affect its biological performance. The team chose to focus on three characteristics: body mass, tooth height and loph count (the number of ridges on molars).

Each of these traits exhibits a relationship based on the degree to which an environment is dominated by grasses versus woody plants. For example, if an animal has a taller tooth, it can more durably consume the abrasive, grassy vegetation of grasslands. With a shorter tooth, an animal is, instead, suited to eat softer, woody vegetation, such as shrubs.

For each of the three traits, the researchers built a model of the trait–environment relationships, estimating what the surrounding vegetation was like in each mammal community over time; specifically, the percentage of shrubs and trees versus grasslands.

Using their ecometric framework, the researchers uncovered a key difference between the mammal biodiversity declines that occurred before approximately 1.7 million years ago and those that occurred after. While biodiversity began declining around 5 million years ago, trait–environment relationships remained consistent despite that loss.

Earlier biodiversity losses were a result of species adapting to grassland environments or tracking their preferred environments across geographies. In short, those biodiversity losses didn’t necessarily have any sort of negative impact on the ability of mammal communities to function properly in their environments.

But later, around 1.7 million years ago, when climates became more arid and variable and tree cover declined to below 35%, a major shift occurred. Rapid losses in the number and variety of species happened, along with a significant disruption in trait–environment relationships. The researchers’ findings suggest that, unlike prior biodiversity losses, those occurring over the past 1.7 million years likely threatened the ability for many mammal species to function well in local environmental conditions.

These findings have important implications for the types of climatic and environmental changes that could affect mammals going forward. In the past, when changes were gradual and wildlife was able to move freely on the landscape, animals could readily adapt.

Today, fragmentation of wildlife habitats by cities, fences and roadways and the fast pace and increasing variability of today’s climate puts animals at risk of losing their ability to function properly in their local environments. So, not all biodiversity losses are the same.

The scientific team hopes that their analysis can shed light on which mammal communities should be prioritized for future conservation efforts. Preference should be given to those most at risk; the communities for whom future biodiversity losses will profoundly affect their ability to adapt and function properly.

Elephants as gardeners of the forests

African forest elephants are one of those mammal communities that are most at risk—and that are architects of their own environments. The pachyderms play a key role in creating forests that store more atmospheric carbon and maintain more biodiversity than forests without elephants. If the already critically endangered elephants become extinct, the rain forests of Central and West Africa would lose between 6% and 9% of their ability to capture atmospheric carbon, amplifying planetary warming.

In a paper published in January 2023 in the journal Proceedings of the National Academy of Sciences, researchers from Missouri’s Saint Louis University document exactly how the ecology of megaherbivores has such a strong influence on carbon retention in African rain forests.

Hunted by humans for millennia, African forest elephants are critically endangered. Shifting the argument for forest elephant conservation from “everyone loves elephants” to the role the animals play in maintaining the biodiversity of the forest hasn’t worked either, say the researchers, as African forest elephant numbers continue to fall. But if we can shift attention to climate change mitigation, perhaps we can generate the support needed for the animals’ conservation. The role of forest elephants in our global environment is too important to ignore, the scientists state.

Within the forest, some trees have light wood (low-carbon-density trees) while others make heavy wood (high-carbon-density trees). Low-carbon-density trees grow quickly, rising above other plants and trees to get to the sunlight. Meanwhile, high-carbon-density trees grow slowly, needing less sunlight and capable of growing in shade. Elephants and other megaherbivores affect the abundance of these trees by feeding more heavily on the low-carbon-density trees, which are more nutritious and palatable than the high-carbon-density species. This “thins” the forest, much like a forester would do to promote growth of preferred species. This thinning reduces competition among trees and provides more light, soil nutrients and space to help the high-carbon trees flourish.

Elephants are also excellent dispersers of the seeds of high-carbon-density trees. These trees often produce large, nutritious fruits which elephants eat. Those seeds pass through the elephants’ guts undamaged; and when they are released through dung, they are primed to germinate and grow into some of the largest trees in the forest.

Due to their taste tendencies, elephants are directly tied to influencing the carbon levels in the atmosphere. High-carbon-density trees store more carbon from the atmosphere in their wood than low-carbon-density trees, helping combat global warming.

Armed with this vital information, we can argue that the importance of conserving the forest elephants of Central and West Africa has never been greater. Populations of African forest elephants have been eliminated from many areas; and in some places, they are functionally extinct, meaning that their populations are so low that they have no significant impact on the ecology of the forest. That is a huge loss for the future viability of the planet.

Wildlife welfare as protection of the planet

The research on Earth’s true architects provides new insights for biodiversity conservation and ecosystem restoration. Rewilding and species reintroduction projects, such as restoring beavers to wetlands and bringing wolves back to Yellowstone National Park, show how harnessing and respecting the natural processes that wild animals provide could help counter some of our biggest environmental challenges, such as climate change, deforestation and whiplash cycles of droughts and flooding.

Helping wild animals thrive is, in the end, saving us and the planet.

Here’s to finding your true places and natural habitats,

Candy