Why Conservation Can No Longer Ignore Apex Species

Editor’s note: The views expressed here are Peter Kareiva’s and should not be taken as the position of The Nature Conservancy.

Conservation folklore has it that losing a species creates a cascade of negative effects for an ecosystem, tearing at its delicate web of life. Data tell a different story. Usually, species loss creates minimal impacts on how well an ecosystem functions, unless we’re talking about the loss of many species — say, 50% of a given ecosystem.

But there are some species whose removal alters their ecosystem so drastically that even the most casual observer can see the difference. Most typically, these species are what scientists call “apex consumers” (also known as “apex predators”) — species that exist at or near the top of their food chains, such as wolves, sharks, bears, foxes and sea otters. The loss of so-called “megaherbivores” such as wildebeest and elephants can also have dramatic effects.

But while ecologists have long known that apex consumers and megaherbivores are special, biodiversity conservation has rarely given them special attention. Why the neglect? Because protecting biodiversity is often turned into a “number of species” game — save the places with the most species. However, all species are not created equal — and it is wrong to invest equally in all species.

A path-breaking article just published in Science may change all that. Two dozen of the world’s leading ecological scientists have synthesized their career knowledge studying apex consumers. The result is a tour de force, and the message for conservation is clear: Biodiversity loss in the abstract and numerical sense is NOT the problem. Biodiversity has been depleted before and then recovered. Similarly, it is being depleted now and will likely recover again. The problem is that the extinction process being driven by humans today is targeting apex consumers and megaherbivores, and thus is a much bigger deal than some “percent decline in biodiversity.”

In the article, Jim Estes and his dream team of star ecologists examine nine case studies in which the effects of losing top consumers are depicted via a series of photographic contrasts: with and without the apex consumer. These pictures are astonishing in how vividly they display altered ecosystems. Of course, they also present detailed measurements of ecosystem change, but the photos speak volumes about the magnitude and extent of the effects. Without these large top predators, rates of infectious disease, wildfires, and carbon emissions can skyrocket. Losing them can also cause degradation in vegetation, water quality and nutrient cycles, according to the authors.

Take one example from Yellowstone National Park, where eliminating wolves led to an explosion in the elk population, which then feasted on trees such as willows and aspen that shaded the park’s rivers. The lack of trees led to declines in species that lived in or along the rivers, such as beavers, birds and fish. Reintroducing wolves to Yellowstone, conversely, allowed these species to recover, and full ecosystem function to return.

Conservation has rallied around many different goals: lands and waters, zero extinction, biodiversity hotspots, charismatic species, and (most recently) ecosystem services. It is a mistake to think there is any one goal for conservation, because goals are human choices — they might be informed by science, but in the end they reflect human values and preferences. To the extent that science does inform our conservation goals, the article by Jim Estes makes a compelling case for making the protection and restoration of apex consumers one of our highest priorities.

Imagine a new conservation NGO with the goal of protecting or restoring the apex consumers in all of the world’s major ecosystem types — so that at least one representation of every ecosystem or habitat type had its full complement of apex consumers. That conservation goal would be easy to track and observe progress (unlike the Convention on Biodiversity’s goal of “slowing the rate of biodiversity loss,” which is problematic to measure, scientifically dicey, and has thus far been impossible to achieve). The goal would inevitably lead to large intact ecosystems. The goal could still accommodate human activities (witness the reintroduction of wolves and grizzly bears into the Great Yellowstone ecosystem). And the goal would inspire many. Can conservation claim as much for its current goals? And do we have such iconic species to define and promote what we are trying to accomplish?

I know that apex consumers aren’t the only things conservation needs to be concerned with. But the article by Jim Estes and colleagues should lead us to give more resources and explicit attention to protecting and restoring these species. They are the next best thing to a holy grail for our work.

(Image: Wolf at Yellowstone Grizzly and Wolf Discovery Center. Image credit: WSK_2005/Flickr through a Creative Commons license.)

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  1. Awesome strawman. On Wikipedia, the statement

    “But while ecologists have long known that apex consumers and megaherbivores are special, biodiversity conservation has rarely given them special attention.”

    would draw a [citation needed].

    And basing your whole argument on a journal article most people can’t access?


  2. The argument on behalf of large animals, predators included, is one that some of the Science team’s members, like Michael Soule and John Terborgh, have been making for more than twenty years. It has become an accepted part of Conservation Biology 101. The Nature Conservancy should start to incorporate this objective into its conservation agreements with those ranchers and governmental agencies who have traditionally been the mortal enemies of these creatures.

  3. I could not agree more with this blog post. Excellent thinking and writing.

    Matt Miller
    I am an employee of The Nature Conservancy

  4. Some parts of this blog, as well as several other interpretations of these research papers requires a word of caution.
    The impact of certain species, especially apex consumers is clear. Conserving these impact organisms certainly warrants greater attention than other species. What is getting overlooked is that this research shows that restoring or reintroducing those same impact organisms warrants the same amount of concern.

    I love Yellowstone, but it is an ecological anomaly and cannot be used to represent the larger part of the world that supports human populations. Yellowstone is a case of preservation, not conservation. It is a place where we pretend that the world is not influenced by humans. Sure Yellowstone has people, but their ecological impact is heavily regulated. They cannot hunt, farm, or build houses in the park. In most of the world, human-caused extinction of apex predators have not left a predator void. In most of the world, humans serve the ecological role of apex predators – not so in Yellowstone. I do wish we could preserve more of the planet, as we have in Yellowstone, but unless we take significant human population reductions, a world of Yellowstones is nothing more than a pipe dream. We need to pay more attention to studies that account for the effects of humans, instead of pretending that the world could be a big Yellowstone.

    Many of the areas affected by wolf reintroductions have not been conservation successes. Megaherbivore populations have plummeted in several areas. Those population drops have driven a huge drop in conservation related revenue. Hunters, their families, and others who spend millions of dollars annually conserving megaherbivores are pulling out of wolf areas. The loss of hunters is only good news for the short-sighted. Whatever the method, removing casual or recreational hunting has historically caused massive losses of wildlife. Why? Well, the answers are in the research. Apex organisms cannot be added or removed from an ecosystem without significant impacts. Replacing one apex organism with another reduces the impact. Humans are an apex organism.

    The bottom line is that conservation needs to actively consider how much humans have replaced apex organisms before jumping into reintroductions of extirpated populations.

  5. Thought-provoking article. So we’re back to charismatic megafauna?

  6. Definitely thought provoking as RKB said…If indeed the most efficient and effective method to save systems is to save apex species, the next question would be how best to categorize, rank, and identify “apex species”…I think that this task is more difficult than it seems…

  7. It seems obvious that “apex predators” have a vital role in their ecosystem. Several species of Tigers are already extincted and I’m pretty sure they had a huge impact in the ecosystem.

  8. The claim that “biodiversity conservation has rarely given [apex predators] special attention” is utterly ridiculous. It is ludicrous. Conservation of top predators has been a core goal of conservation scientists and groups since the beginning of the modern environmental movement in the 1960s. Indeed, they’ve regularly (and not without reason) been criticized for devoting too much attention to them in the face of a broader extinction crisis wiping out reptiles, amphibians and freshwater fish and invertebrates.

    Whether one agrees with the distribution of resources between apex predators and other species; no one with even the slightest knowledge of modern conservation can agree that apex predators have been ignored.

    Peter is either so megalomaniacal, that he feel himself exempt from basic scholarly ethics; or he is so divorced from conservation in his TNC white tower he really doesn’t know what conservationists do. I’m afraid that both are probably true.

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