Biological annihilation

Catarina pupfish

No bells tolled when the last Catarina pupfish on Earth died. Newspapers didn't carry the story when the Christmas Island pipistrelle vanished forever.

Two vertebrate species go extinct every year on average, but few people notice, perhaps because the rate seems relatively slow - not a clear and present threat to the natural systems we depend on. This view overlooks trends of extreme decline in animal populations, which tell a more dire story with cascading consequences.

In a new publication researchers from Stanford University and UNAM in Mexico City draw a bleak picture of the future by talking about biological annihilation in an ongoing sixth mass extinction. The new study looks beyond species extinctions to provide a picture of dwindling populations and ranges. The colleagues mapped the ranges of 27,600 species of birds, amphibians, mammals and reptiles (nearly half of known terrestrial vertebrate species) and analyzed population losses in a sample of 177 well-studied mammal species between 1990 and 2015.

It turns out that more than 30% of vertebrate species are declining in population size and range. Of the subset mammals for which the researchers had detailed data, all have lost 30% or more of their geographic ranges and more than 40% of them have actually lost more than 80% of their ranges, most of which in southeast Asia. In general tropical regions have had the greatest number of decreasing species while temperate regions have seen similar or higher proportions of decreasing species. The study's mapping exercise suggests that as much as 50% of the number of animal individuals that once shared Earth have disappeared, as have billions of animal populations.

This is the case of a biological annihilation occurring globally, even if the species these populations belong to are still present somewhere on Earth... The massive loss of populations and species reflects our lack of empathy to all the wild species that have been our companions since our origins. It is a prelude to the disappearance of many more species and the decline of natural systems that make civilization possible.

What concerns me even more is the fact that this paper and many other studies exclusively look at vertrebrate species which are among the least diverse groups of animals. What about invertebrate diversity? Unfortunately, there is only anecdotal data and evidence. Humans haven't amassed much data to have a closer look but it is likely very similar if not worse. Few reliable data exist on the fate of important insect species. Scientists have tracked alarming declines in domesticated honey bees, monarch butterflies, and lightning bugs. But few have paid attention to the moths, hover flies, beetles, and countless other insects that buzz and flitter through the warm months. A recent article in Science gives a glimpse of what is going on in the invertebrate world. If we want to use such strong language as biological annihilation or erosion of biodiversity we might want to look a bit closer at the bugs around us even if the insights we gain might be even more disturbing that what we already learned from vertebrate studies.