About 25 years ago, David Tilman began to explore biodiversity’s importance.

Working with the University of Minnesota’s Cedar Creek Ecosystem Science Reserve, Tillman and other researchers first thought they would find some significance but underestimated just how important it is.

“Biodiversity matters immensely, much more than we ever imagined,” he said.

Today, Tilman reviews how human growth has historically affected biodiversity. With that data, he predicted a bleak future for Africa’s mammals and birds. His review published in the June 1 biodiversity issue of the scientific journal Nature.

It’s now common knowledge to researchers that biodiversity is important in ecosystems. Diverse species essentially let ecosystems work better on every level — they become more productive and resistant to invasive species.

An ecosystem is comparable to human society, Tilman said, who is now a University Regents professor in the Department of Ecology, Evolution and Behavior. Each species has a certain role, akin to people with specific jobs, Tillman said.

“When [ecosystems] lose diversity, they’re basically losing these long-term evolved professions … and therefore with those, they don’t perform as well,” Tilman said.

His review for Nature predicted a population explosion in Africa and continued poor agricultural practices, which puts several species face-to-face with high risks of extinction.

Tilman worked with Craig Packer, director of the University’s Lion Research Center, on the review.

Packer said most research focuses on past and present issues in biodiversity.

“What we wanted to point out is that there’s a pressing need to anticipate and deal with the expected growth in human populations, especially in Africa,” he said.

Weighing human costs

The population boom in Africa will mean more mouths to feed, Tillman said, and more land cleared for farming.

Clearing land is the main way humans cause species extinction.

But protecting land without addressing why people use it is immoral, he said.

“With conservation you really do have to keep in mind what’s going on with the people who live there as well,” Packer said.

Tilman’s main solution to this issue is to increase efficiency of farmland. With farming practices like using better seed and fertilizer, populations can keep land usage low for their food production.

However, the countries where this is needed most lack the funding and education to properly institute these changes, he said.

“Those practices can increase the food production so much that most African nations would never need to clear any land even though they might have three or four or five times their current food demand,” he said.

Tilman and Packer suggested other ways to tackle this problem could be made through societal diet changes or by changing how countries trade crops.

If a developed country like the U.S. were to cut its consumption of animal products like meat and eggs, it would open the door to export more crops to underdeveloped countries, Tillman said.

Certain areas of the world are better for growing certain crops, Tillman said.

If these high-yield countries exported to low-yield countries, whose existing cropland could be used for better-suited crops, they think it could decrease the amount of land needed to feed the world’s population, he said.

Biodiversity’s complex human connection

Alongside Tilman’s review in Nature, Forest Isbell, associate director of the Cedar Creek Ecosystem Science Reserve, published a review of how humans benefit from biodiversity even as their practices harm it.

Human practices like nutrient pollution, overharvesting animal populations and introducing invasive species can all harm biodiversity — along with humans’ role in climate change, Isbell said.

Isbell said biodiversity aids humans by contributing to what scientists call “ecosystem services,” like the production of wood, crops and fish.

Economically, this means humans can invest financially into conserving biodiversity and see returns from the increased productivity of these services, he said.

“It’s quite clear that human activities are undermining our ability to continue receiving these benefits from nature,” said Isbell, who is also a professor in the Department of Ecology, Evolution and Behavior.

Isbell’s review found the benefits of preserving land are greater than the benefits of turning land into cropland, economically.

Preserved land slows the effects of climate change better than cropland, he said.

The adverse effects of climate change include rising sea levels and disruption of fisheries — both of which are more costly than they are worth, he said.

A hopeful future

Both Isbell and Tilman’s reviews glanced into the future and found some hope.

Isbell said there is a long delay between when a habitat is disturbed and when the last individual of a species dies.

Tilman’s review noted that, if the efficiency of farming practices across the world improve, there would be enough food to feed a global population of 10 billion without massive damage to biodiversity.

“We can act over the next few decades and restore ecosystems, increase the abundances of these species and give them a good chance of persisting,” Isbell said.