Rats are among the alien species which have caused global extinctions. Pictured: Rats eat grains of puffed rice in Allahabad on July 28, 2015. Getty Images/Sanjay Kanojia

Maybe it's a good thing we haven't made contact with aliens yet — they might cause the extinction of the human race.

This is what is happening at the moment around the globe, with alien species, or those not native to a particular environment, being the primary cause of the recent extinctions in both animals and plants, a new study suggests. UCL researchers wrote in the new paper published in the scientific journal Frontiers in Ecology and the Environment that alien species have been "solely responsible" for 126 extinctions, or 13 percent of the total number of extinctions studied, since 1500.

Alien species also played some role in about 300 of the 953 global extinctions. Of the 300 extinctions, researchers noted that 42 percent had alien species alone listed as the reason for their eradication, based on data from the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. This inventory lists all species considered to have died off around the world since 1500.

"Some people have suggested that aliens are no more likely than native species to cause species to disappear in the current global extinction crisis, but our analysis shows that aliens are much more of a problem in this regard," lead researcher Professor Tim Blackburn of UCL Biosciences, said in a statement.

"Our study provides a new line of evidence showing that the biogeographical origin of a species matters for its impacts," he continued. "The invasion of an alien species is often enough to cause native species to go extinct, whereas we found no evidence for native species being the sole driver of extinction of other natives in any case."

Of the 782 animal species that have been wiped out, 261 were forced into extinction by aliens, while 39 out of the 153 species have been eradicated by the same cause. In contrast, native species caused 2.7 percent of animal extinctions and 4.6 percent of plants.

Among the alien species listed by the IUCN to have caused extinctions are "black, brown and Pacific rats and feral cats, with island habitats hit the hardest." Some of the alien animals, like the foxes and cats, were "introduced deliberately," while others invaded by stowing away on boats.

According to the statement, many of the alien plant species were also "intentionally introduced."

Blackburn explained that they considered some of the species whose origins were unknown as native, though they would be more realistically considered alien. With that said, he believes that the results are "conservative" in terms of how much they blamed alien species for the extinction of many animals and plants worldwide.

Blackburn added that there may be more extinctions that could be added to the list as many regions around the globe have yet to be explored and studied.