The Amazon rainforest, according to a 2021 study, is losing its capacity as a carbon sink and now emits more than it absorbs. In the tropics, marine scientists are reporting that coral reefs are in decline, threatening fish stocks. Equally concerning is research into the Atlantic Meridional Overturning Circulation (Amoc), a vast system of ocean currents that helps regulate the climate and is at risk of collapsing this century. The entire global ecosystem appears to be losing its ability to function.
We find this view in newspapers, magazines, technical reports and the journals of learned societies. But thinking about the environment in terms of its functions is also how many of us tend to understand the world. We may think that forests exist to produce oxygen, wetlands to filter water and bees to pollinate our crops.
There is a problem with this way of thinking: ecosystems don’t exist to perform goals. The Amazon absorbs carbon, but it doesn’t “aim” to do so. It simply exists. Any standards of operation we find in nature have come directly from our own desires for things such as climate stability, abundant fisheries, beauty or cultural meaning.
So why do we keep thinking ecosystems have functions they could fail to perform?
I came to this puzzle as a graduate student in the late 1990s, a time when research into biodiversity and ecosystem function was rapidly increasing. Initially, I thought I would write my dissertation on a conventional ecological topic: whether species richness drives productivity. Instead, I fell in with the philosophy of science crowd, attended their seminars and eventually earned a master’s degree in philosophy alongside my work in ecology. There I encountered a rich debate over the concept of function – what it means, when it applies, what work it does. But no one seemed to be connecting that debate to the way ecologists were using the same word, unreflectively, to describe what ecosystems do. This essay is an attempt to bring those conversations together.
My concern with ecosystems and function was never just academic. I am an environmentalist, unsettled by the loss of natural places. And as a father, I am concerned that my generation will leave to our children a planet depleted in both richness and resilience. These commitments also drive my interest in debates about function. If the way we think about ecological crisis is conceptually shaky, we risk obscuring what’s really at stake.
I worry that the ways we often conceive of the problems before us are inadequate. For if ecosystems have no intrinsic ends and cannot truly “break down”, how do we repair them? How do we respond to environmental crises in a world of aimless ecosystems?
Approaches to conservation have long been shaped by debates about whether nature has a purpose or whether we are projecting our own aims on to it. Behind every attempt to justify new protections lies an implicit answer to the question: what is the environment for?
In the United States and the United Kingdom during the 19th century, these answers were rooted in game laws and hunting traditions that sought to maintain populations of species valued for sport or resource use. By the mid-20th century, the American forester and early conservationist Aldo Leopold offered a more expanded answer by proposing that our moral community should include “the land” itself: soils, waters, plants and animals.
In the 1970s and 80s, the answers of conservationists were increasingly grounded in the intrinsic value of specific species, reflected in legislation such as the US Endangered Species Act. But a decade later, the species-focused approach of “conservation biology” was seen by many as lacking. It targeted only rare organisms that contributed little to the circulation of their ecosystems – species such as the spotted owl and the snail darter fish. Some researchers worried that the species approach might have overlooked more consequential concerns, including the major “services” provided by ecosystems, such as food production, clean water, drought mitigation, storm protection, timber and fibre.
In the late 1990s, this crisis led to a new research agenda, which crystallised around “biodiversity and ecosystem function” (BEF). This approach presented itself as a scientifically rigorous framework while serving as a rhetorically powerful justification for conservation. In contrast to a hyper-focus on individual populations of rare species, BEF embraced all biodiversity.
In the early decades of the 21st century, this logic scaled up, underpinning UN projects and intergovernmental science policy. National governments began commissioning natural-capital accounts, attempting to assign monetary value to pollination, flood regulation, carbon storage and other ecological phenomena. The answer to the question “What is nature for?” had become this: nature is for the services it provides to people. The language of ecosystem function was the conceptual bridge that made this answer sound scientific rather than merely political.
As a result, the idea of function now pervades how ecosystems are described and understood. Consider for a moment how you think about the ecosystems around you. If you have ever described a forest as a carbon sink or a wetland as a natural filter, you have inherited the ethic of BEF. If you’ve ever thought of a rainforest as something that provides oxygen for humans, or a reef as something that helps furnish us with protein (in the form of fish), you’ve inherited the logic of “ecosystem services”.
What do we mean when we use the word “function”? Sometimes, it refers to designed purposes. For example, when we say that the function of a clock is to tell the time, or the function of a carburettor is to mix air and fuel for combustion. In these cases, the object (or one of its parts) was intentionally made for a specific end. The same logic applies up a hierarchy of wholes and parts: the carburettor is part of the engine, the engine part of the car, the car part of a transport system.
Other kinds of functions arise through co-option rather than design. Writing at a picnic table, I might use a book or a rock to keep my papers from blowing away. The rock was not designed and the book was intended for another purpose, yet both can serve the goal I have in mind. I give them their function by using them in a certain way.
Still other functions emerge without any intention, particularly in nature. The philosopher Karen Neander offers a striking example: penguins are myopic on land. Their eyes are not defective but optimised for underwater focus, where penguins feed. Land myopia is a byproduct of a visual system shaped for a different environment.