Drivers of Extinction
Updated: May 25, 2021
It is not difficult – by no means rocket science – to discern the most important cause of this Sixth Extinction I discussed in the previous post. It is, of course, us. But, more importantly, it is something we do.
IPBES – the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services – is, let’s face it, a bit of a mouthful. IPBES is to extinction what the IPCC (the Intergovernmental Panel on Climate Change – slightly less of a mouthful but still not particularly catchy) is to climate change. In 2019, IPBES released their long-awaited Global Assessment Report, in which they list the most important drivers of extinction.
These drivers have increased dramatically in force and scope during the past fifty years. The direct drivers of species extinction, in order of importance, are: (1) changes in land use and sea use, (2) direct exploitation of organisms, (3) climate change, (4) pollution and (5) invasion of alien species. Indirect drivers of extinction are, essentially, those that are ultimately responsible for the direct drivers. These include, “production and consumption patterns, human population dynamics and trends, trade, technological innovations and local through global governance.”
The two main causes of species extinction, therefore, are changes in land and sea use, and direct exploitation of organisms. The expression direct exploitation refers to hunting of animals – terrestrial or marine – for their meat or other products. In the case of marine animals, (1) and (2) are reversed: fishing is the primary cause of marine species extinction. On land, however, change in land use is the primary driver of reallocation-extinction, followed by hunting.
Change in land use can be the result of several factors. Urban development and the expansion of infrastructure linked to a growing population and increased consumption can obviously be one of those factors. However, it is not the most important. That accolade belongs to agriculture. The IPBES report tells us that, “Agricultural expansion is the most widespread form of land-use change, with over one third of the terrestrial land surface being used for cropping or animal husbandry.” The report also notes that this change in land use has come, “mostly at the expense of forests (largely old-growth, tropical forests), wetlands and grasslands.”
To summarize: on land, the number one driver of species extinction lies in changes in land use, and the number one reason for change in land use is agricultural expansion.
Agriculture is, of course, both arable and pastoral. However, due to well-known feed-conversion ratios of vegetable into animal matter – pastoral farming utilizes far more land, and most change in land use is, accordingly, driven by pastoral farming. Ground Zero for change in land use is, sill, almost certainly, Brazil. In the Amazon rainforest, according to the Satellite Legal Amazon Deforestation Monitoring Project, almost 10,000 square kilometers, or 3800 square miles, or 2,432,000 acres were lost to deforestation in the year August 2018 to August 2019. Seventy percent of this deforested land is used as pasture, with animal feed crop cultivation occupying much of the remainder.
The conclusion seems inescapable. If, as IPBES tells us, (1) changes in land use are the number one factor in driving species extinction, and if, as IPBES also mentions, (2) the number one factor driving changes in land use is agricultural expansion, and if (3) by far the predominant form of agricultural expansion is in pastoral or animal farming, together with the growing of feed crops to support this animal farming, then we can conclude that (4) the most important factor driving the extinction of terrestrial species is expansion in animal agriculture.