This year, we learned that wildlife populations around the world have plummeted by 60 percent in just 40 years. Largely thanks to human activity, iconic creatures from vast elephants to teeny tiny bees are being lost at a troubling rate. But what effects do dwindling populations have on the animals themselves?

A new study, published in the journal Current Biology, has found that the critically endangered Grauer’s gorilla has lost so much genetic diversity in recent years that the apes are suffering from harmful genetic mutations. Essentially, fewer gorillas mean less diversity within a population and more inbreeding, leading to genetic problems in the next generation.

Also known as the eastern lowland gorilla, the Grauer’s gorilla (Gorilla beringei graueri) is a subspecies of eastern gorilla found only in the mountainous forests in the east of the Democratic Republic of Congo. It is currently listed as critically endangered by the International Union for Conservation of Nature (IUCN) thanks to human pressures like habitat destruction and poaching, which have caused populations to plummet by 80 percent in recent decades.

To see how this decline has affected the genetic health of the gorillas, a team of researchers from Uppsala University in Sweden and the Swedish Museum of Natural History analyzed the genomes of gorillas that lived up to 100 years ago and compared them with the genomes of those alive today.

They found that over the decades, Grauer’s gorillas have become more inbred and lost a significant amount of genetic diversity. Harmful genetic mutations that have increased in frequency include those linked to reduced disease resistance and male fertility. The team also found signs of mutations linked to a loss of function in the genes involved in the healthy development of fingers and toes, explaining why some of today’s gorillas appear to have webbed hands and feet as their digits are fused together.

“This recent increase in harmful mutations really emphasises the need to reverse the ongoing population decline in Grauer’s gorillas,” said Love Dalén of the Swedish Museum of Natural History in a statement.

The team also looked at the genomes of mountain gorillas, which are closely related to Grauer’s gorillas. However, they found that these gorillas haven’t experienced the same loss of genetic diversity and increase in harmful mutations. The authors posit that this might be because mountain gorillas have been very rare for thousands of years and have therefore lost harmful mutations thanks to natural selection, whereas Grauer’s gorilla numbers dramatically increased between 5,000 and 10,000 years ago.

Allowing the number of Grauer’s gorillas to expand is key to their conservation as it will allow their genetic diversity to increase once more. And there’s something you can do to help. Illegal mining for metals used in cell phones in the gorillas’ habitat is adding to their demise, so be sure to always recycle your old cell phones to lessen the demand.