29/09/2020

Invasive species

 

“HUMAN BEINGS have overrun the world.” So laments Sir David Attenborough, a world-famous nonagenarian naturalist, in his new film, “David Attenborough: A Life on our Planet”. The film charts the “devastating changes” that humans have wrought on the planet’s biodiversity. All told, we have driven at least 680 vertebrate species to extinction since 1500.

Sir David and his followers have cause to be worried. The Living Planet Report, published in September by the WWF, a conservation organisation, found that the world’s populations of wild mammals, birds, amphibians, reptiles and fish have fallen by an average of 68% since 1970. Using data on 20,811 populations of 4,392 animal species, WWF estimated that animal populations fell by 94% on average in Latin America and by 65% in Africa.

Part of the reason why so many animals (and plants, for that matter) are imperilled is that humanity overspends its “biological budget”. The Global Footprint Network, a think-tank, calculates this in terms of the amount of land and sea required to produce the quantities consumed; in the case of greenhouse gases emitted from burning fossil fuels, the impact is expressed in terms of the amount of land needed to absorb those emissions. Since 1970 humanity’s ecological footprint has exceeded the planet’s natural rate of renewal. According to the think-tank, people currently consume 1.6 times more resources than the Earth can regenerate. Most of the impact comes from carbon usage, which accounts for 60% of people’s ecological footprint. Repurposing land for crops (19%) and cutting down trees for fuel, pulp and timber (10%) also contribute to the ecological deficit.

Rich countries are the worst offenders. The report calculates that the average person in the world uses around 2.5 hectares of land or sea to sustain their consumption habits (a sustainable amount would be 1.6 hectares each). But much of Europe, North America and Australia use an average of more than five global hectares per person, whereas India and much of Africa use less than 1.6.

Covid-19 has sharpened green campaigners’ focus on the dangers of zoonotic diseases (ie, those transmitted by animals). The WWF report points out that “nearly half of all new emerging infectious diseases from animals are linked to land-use change, agricultural intensification and the food industry.” The loss of biodiversity is also linked to economic and security risks; in developing countries, competition over increasingly scarce natural resources can lead to conflict. Sir David puts it plainly: “The way we humans live on Earth is sending it into a decline.”

This article is from our Graphic detail section.