Genetic diversity among animals and plants has declined worldwide over the past 30 years, according to an analysis of more than 600 species.

Published in Nature, the study revealed decreases in genetic diversity in two-thirds of the populations examined. However, researchers emphasised that targeted conservation efforts could stop or even reverse these losses.

An international team of scientists reviewed 882 studies measuring genetic diversity changes from 1985 to 2019 across 628 species, including animals, plants, fungi, and chromists (a group of organisms). They described it as “the most comprehensive investigation” of genetic diversity changes within species to date.

Lead researcher Assoc. Prof. Catherine Grueber from the University of Sydney explained that genetic diversity within a species—variations among individuals—helps populations adapt to environmental changes. Preserving genetic diversity is crucial for species’ long-term survival and was a key target of the 2022 Cop15 biodiversity conference.

“If a new disease comes through, or there’s a heatwave, there may be some individuals in the population that have certain characteristics that enable them to tolerate those new conditions,” she said.

“Those characteristics will get passed on to the next generation, and the population will persist instead of going extinct.”

The study found that many causes of genetic diversity loss overlap with factors driving population declines, such as habitat destruction and human exploitation.

Grueber said, “Things like habitat loss, climate change, invasive species, new diseases.”

Ecological disturbances were detected in 65% of the populations, including human harvesting, harassment, and land-use changes.

Surprisingly, genetic diversity losses were observed even in undisturbed habitats, suggesting an underlying “background level” of decline.

“We think that this represents the more general biodiversity crisis that the planet is facing, and broader effects of ecological disruptions [such as] climate change,” Grueber said.

Despite the concerning trend, the researchers highlighted successful conservation efforts that have enhanced genetic diversity. For example, in Western Australia, new populations of golden bandicoots—a threatened species—were established to bolster their genetic pool.

“By understanding where they were selecting the animals from … and monitoring those populations using genetic studies, they were able to show that they could maintain the genetic diversity of those populations through multiple generations,” Grueber said.

In the US, conservation biologists protected genetic variability in black-tailed prairie dogs by treating them with insecticides, preventing flea-borne plague outbreaks.

“The populations were able to thrive, and by moving around more in the landscape, they were able to interbreed with other prairie dogs,” Grueber said.

Meanwhile, in Scandinavia, arctic fox populations faced competition from red foxes after their numbers were diminished by the fur trade. Conservationists improved genetic diversity by providing supplemental food and managing red fox numbers.

“It’s important that we preserve the genetic diversity of our natural systems,” Grueber said. “We have the methods to make it work.”

The meta-analysis covered species from 141 countries, including over 500 animal species, offering a broad perspective on global genetic diversity trends. The findings underscore the importance of proactive and tailored conservation strategies to maintain biodiversity.