New publication shows how overpopulation drives biodiversity loss

By The Editors | 19 July 2022
The Overpopulation Project

The concept of human overpopulation, once common, is now rarely used in the scientific literature. Yet overpopulation is a major driver of biodiversity loss and a key obstacle to fairly sharing habitat and resources with other species. A new publication from TOP explores the connections between human numbers and preserving wild nature.

“Overpopulation is a major cause of biodiversity loss and smaller human populations are necessary to preserve what is left.” That’s the title of a new article by Phil, Pernilla and Frank just published in Biological Conservation. Those working to protect wild nature, including conservation scientists, rarely advocate for smaller human populations. Speaking out about population matters can be challenging; in fact, the journal’s editor has already fielded several complaints for publishing the article. But failure to address the root causes of biodiversity loss will doom conservationists’ efforts. Successfully protecting Earth’s remaining biodiversity requires challenging growth and reducing the excessive size of human populations and human economies, which are intimately connected.

Overpopulation is a major cause of biodiversity loss and smaller human… https://t.co/ai38eTKSZB READ SLOWLY TO GEORGE MONBIOT
— Paul R. Ehrlich (@PaulREhrlich) July 14, 2022

Global biodiversity decline is best understood as too many people consuming and producing too much, thus displacing other species. Wild landscapes and seascapes are replaced with people, our livestock and crops, our economic support systems, and our trash. Conservation biologists standardly list five main direct drivers of biodiversity loss: habitat loss, overexploitation of species, pollution, invasive species, and climate change. All five direct drivers are important, on land and at sea. As we show in our article, all are made worse by larger and denser human populations.

Just as population increases clearly contribute to biodiversity losses, so population decreases aid in restoring biodiversity. All else being equal, smaller human numbers open more space for wild species. One sees this particularly clearly in Europe, densely populated, but also the first continent to end humanity’s modern population explosion. Europe’s overall population has stabilized in recent years and its rural population has declined 20% since 1960, contributing to extensive abandonment of less productive farmland. These trends have been valuable for wildlife, particularly larger herbivores and carnivores, which have naturally recolonized many former agricultural areas. Ecological restoration can accelerate these trends, turning what is often viewed as a negative (“rural depopulation”) into a positive (“rewilding” the landscape and restoring a country’s natural heritage). In certain habitats low-intensity traditional management is favorable for plants, insects and birds; such management should be encouraged as part of rewilding efforts, also creating jobs for people in rural areas.

Restoring Abandoned Land in the Oder Delta Gives New Opportunities for Wildlife in Germany and Poland https://t.co/C2nx79wjtC via @TheOverpoplat1
— The Overpopulation Project (@TheOverpopulat1) April 9, 2020

The article goes on to discuss opportunities for further research into how human demographic changes help or hinder conservation efforts. Most conservation biologists believe that greatly increasing the amount of land and seas in protected areas is necessary to preserve Earth’s remaining biodiversity. But the role of population reduction in achieving the goals of Half Earth or similar proposals remains largely unexplored. So does the role of population increase in closing off conservation options. How much of Germany or India, Mexico or New Zealand, would have to be set aside to preserve viable populations of their remaining native wildlife—and how large a human population would be compatible with this goal? How much of Africa’s megafauna can remain if the human population on the continent increases from 1.4 to 3.9 billion by 2100, as forecasted in the new United Nations population projections—and how much more could be saved if African nations provided their citizens with universal access to modern contraception and family planning services? For now, we can only guess at the answers. Conservation biologists could do better.

Finally, the article argues that scientists should advocate for smaller populations, explicitly, because current human numbers are far beyond what is compatible with the preservation of global biodiversity or long-term human wellbeing. In the long term, smaller human populations are necessary to preserve biodiversity in both less developed and more developed parts of the world. Whether the goal is to save threatened species, create more protected areas, restore degraded landscapes, limit climate disruption, or any of the other objectives key to preserving biodiversity, reducing the size of the human population is necessary to achieve it. According to recent United Nations projections, reducing fertility rates half a child below the projected medium (most likely) rate would reduce the global population in 2100 by more than three billion people. The benefits to other species certainly would be substantial.

The world’s population is expected to reach 8 billion on Nov. 15, with India set to surpass China as the world’s most populous country next year, according to the latest UN World Population Prospects report. https://t.co/TX7qFCaUz4 pic.twitter.com/ZTUnJOjduM
— Jeffrey Kleintop (@JeffreyKleintop) July 19, 2022

The number of children people have should always be an informed personal choice. It is important that the decision is responsible, with respect to existing children, our communities, future generations, ecosystems, and wild species. If scientists are silent on this issue, parents (and governments) receive only the growthist propaganda of business lobbies. Fortunately, scientists have begun to speak up on the need for population reduction to achieve real ecological sustainability. Conservation biologists, motivated by love for the natural world, should lend their voices to those calls.

During the past hundred years, Homo sapiens’ population increased from 2 billion to nearly 8 billion and the United Nations projects an increase to 10.4 billion before 2100, unless steps are taken to reduce this population growth. Ignoring the present high level and this projected increase means ignoring a major driver of the unfolding biodiversity crisis. Accepting current bloated human numbers as an appropriate status quo means accepting a biologically impoverished, and perhaps unlivable, planet. We must do better.

Reprinted with permission from Frank Götmark – Project leader of The Overpopulation Project (TORP); Professor, Animal ecology and Conservation Biology, University of Gothenburg.