What is the scale of biodiversity loss?

The list of known recent extinctions is still a small fraction of all species on the planet but it is far above prehuman levels and the evidence suggests it is rising fast. A recent report indicated that one million species could be threatened with extinction. Since 1500, 1.6% of birds, 1.9% of mammals and 2.2% of amphibians have been recorded as extinct. Between 1990 and 2020, around 420 million hectares of forest (mainly tropical forest) has been lost and a further 10 million hectares, an area the size of Scotland and Wales combined, is being lost each year.

Extinctions have always occurred but the rate at which they are happening now far exceeds the rates at which species have naturally gone extinct over the course of the fossil record. The historical spread of humanity over the planet has been associated with waves of extinctions in other species. Key threats to date have been over-hunting and harvesting of species by people, habitat conversion and degradation, and the introduction of invasive species caused by human migration, settlement, trade, agriculture and resource extraction. These threats have been accelerating since 1500 alongside rapid growth in human populations and increasing growth in per capita consumption of resources. In addition, in the past few decades, climate change has become an increasingly important threat. Estimates suggest that extinction rates in the recent past have been running tens to hundreds of times faster than in pre-human times and that the pace is accelerating.

In those groups of plants and animals that have been systematically assessed under International Union for Conservation of Nature Red List criteria, about 25% are classified as threatened with extinction (that is, Critically Endangered, Endangered, or Vulnerable). Five groups (mammals, birds, amphibians, corals, and cycads) have been comprehensively assessed two or more times since 1980. In all cases the reassessments show an increasing trend in the proportion of species that are threatened.

Comparing the results of surveys of insects from the 1970s and 1980s to what we have now is helping to create a picture of changes in biodiversity. However, there is a lot more work required to understand these changes and their consequences. 

For more on this topic visit Past and future decline and extinction of species | Royal Society and Consumption patterns and biodiversity