Biodiversity: Species are moving, scientists are perplexed

In 1995, a young American ecologist, Camille Parmesan, was studying an elegant butterfly from the West Coast, Euphydras editha , Edith's checkerspot. Comparing her observations with those of colleagues from the beginning of the century, she noticed that the distribution area (the area occupied by the animal) of her graceful lepidopteran had changed: it was now found much further north and at higher altitudes. An observation that would revolutionize the hitherto relatively static worldview of scientific ecology.

Because the researcher, intrigued, wondered if global warming, which was just beginning to be discussed, was not the cause. To verify this, she joined forces with a team of colleagues from around ten European countries (those with the best historical data on butterflies), who then reviewed thirty-five species. Their work, published in Nature in 1999, was a bolt from the blue: 63% of these species were now found further north than a century ago, from 35 to 240 km, and only 3% further south. The first consequence of global warming on living things had been identified.

Camille Parmesan's work will then be extended, by herself and by others, to thousands of organisms, terrestrial and marine. Showing that the living has started to move, on a very large scale. On all continents, countless microbes, plants, corals, insects, and mammals are in the process of modifying their distribution area, in a sort of immense planetary crisscrossing.

The study of these movements has an obvious theoretical scientific interest: they hold the key to what is important for species, how they move, and how they assemble. But understanding and predicting the future movements of animals, plants or microbes would, moreover, have a major practical interest.

"There are two important areas that will be impacted by these movements: nature conservation and public health," says Veronica Frans, who recently received her doctorate at Michigan State University and was an EEB member. She is now a researcher at Stanford University who published a notable article on these issues in the journal Nature Ecology and Evolution in June 2024.

"Indeed, to define the location of protected areas, it is important to know what species will be there!" she comments. A forest can become ecologically essential or, conversely, an island uninhabitable. "As for health, many diseases, such as malaria, depend on the movements of vector organisms such as mosquitoes. We must therefore know how to model these species movements."

There are at least two other areas where this prediction would be valuable. Agriculture, because many plants and livestock are always interacting, positively or negatively, with wild organisms, whether pollinating insects, meadow plants, or various pests.

And then there is forestry, where there is concern about the speed of global warming. Which trees will survive the future climate, should we let the forests manage to adapt or should we plant them, and in this case which species? To answer these questions, we still need to be able to determine the movements of the distribution areas of the trees...

Read the full translation from French here.