By Gail Gallessich

An international team of scientists has published a new analysis showing that as plant species around the world go extinct, natural habitats become less productive and contain fewer total plants—a situation that could ultimately compromise important benefits humans derive from nature.

“The process by which plants grow and produce more plant biomass is one of the most fundamental biological processes on the planet,” said Bradley Cardinale, lead author of the paper and assistant professor of ecology, evolution, and marine biology at UC Santa Barbara.

Plant productivity regulates the ability of nature to take greenhouse gases, like carbon dioxide, out of the atmosphere, as well as the ability of habitats to produce oxygen, food, fiber, and biofuels, according to the authors of the study. “Therefore, species extinctions could compromise the benefits that nature provides to society,” said Cardinale.

Summarizing the results of 44 experiments from around the world that simulated plant species’ extinction, the study showed that ecosystems with fewer species produce up to 50 percent less plant biomass than those with more “natural” levels of diversity.

“Our analyses provide the most comprehensive evidence yet that natural habitats with a greater variety of plant species are more productive,” said co-author Michel Loreau of McGill University in Montreal. “This occurs partly because diverse communities are more likely to contain highly productive species. But even more important, our analyses show that diverse communities are more productive because plants are ‘complementary’ in how they use biological resources.”

Co-author Andy Hector of the University of Zurich used a soccer analogy to illustrate. “Plant communities operate much like a soccer team,” he said. “Teams are composed of both star players and supporting players. You probably can’t win many games if you lose your top striker because she or he is the most productive player and can dominate a game.”

According to the authors, plant communities are also composed of both stars and supporting players. They said that species extinction is one of the most pronounced environmental changes of our time and noted that many scientists now argue that the Earth is in the middle of the sixth mass extinction in the history of life.

Some estimates suggest that as much as 50 percent of all known species could be extinct by the end of this century.

Cardinale emphasized that experiments to date have probably underestimated the impact of species loss on ecosystems. “We found that as experiments were run longer, they detected increasingly strong impacts of species diversity on plant productivity,” he said.

Other authors of the study, which appear in the Proceedings of the National Academy of Sciences, were: Marc W. Cadotte, Ian T. Carroll, and Jerome J. Weis of UCSB; Justin P. Wright of Duke University; and Diane S. Srivastava of the University of British Columbia.