What is biodiversity and why does it matter to us
The air you breathe, the water you drink and the food you eat all rely on biodiversity, but right now it is in crisis – because of us. What does this mean for our future and can we stop it?
by Damian Carrington Environment editor
Mon 12 Mar 2018 09.33 GMT
It is the variety of life on Earth, in all its forms and all its interactions. If that sounds bewilderingly broad, that’s because it is. Biodiversity is the most complex feature of our planet and it is the most vital. “Without biodiversity, there is no future for humanity,” says Prof David Macdonald, at Oxford University.
The term was coined in 1985 – a contraction of “biological diversity” – but the huge global biodiversity losses now becoming apparent represent a crisis equalling – or quite possibly surpassing – climate change.
More formally, biodiversity is comprised of several levels, starting with genes, then individual species, then communities of creatures and finally entire ecosystems, such as forests or coral reefs, where life interplays with the physical environment. These myriad interactions have made Earth habitable for billions of years.
A more philosophical way of viewing biodiversity is this: it represents the knowledge learned by evolving species over millions of years about how to survive through the vastly varying environmental conditions Earth has experienced. Seen like that, experts warn, humanity is currently “burning the library of life”.
Just how diverse is biodiversity?
Mind-bogglingly diverse. The simplest aspect to consider is species. About 1.7 million species of animals, plants and fungi have been recorded, but there are likely to be 8-9 million and possibly up to 100 million. The heartland of biodiversity is the tropics, which teems with species. In 15 hectares (37 acres) of Borneo forest, for example, there are 700 species of tree – the same number as the whole of North America.
Recent work considering diversity at a genetic level has suggested that creatures thought to be a single species could in some cases actually be dozens. Then add in bacteria and viruses, and the number of distinct organisms may well be in the billions. A single spoonful of soil – which ultimately provides 90% of all food – contains 10,000 to 50,000 different types of bacteria.
The concern is that many species are being lost before we are even aware of them, or the role they play in the circle of life.
Sixth mass extinction
Life on Earth has suffered five mass extinctions of biodiversity in its long history, caused by massive volcanic eruptions, deep ice ages, meteorite impacts and clashing continents. But some scientists believe a sixth mass extinction has now begun.
This one is very different, caused not by geology or natural climate change, but by a single species – us. Humans and our livestock now consume 25-40% of the planet’s entire “primary production”, i.e the energy captured by plants on which all biodiversity depends. We have become a voracious top predator across the entire globe.
One estimate suggests that, by weight, 97% of the world’s vertebrate land animals are now either humans or our farm animals – just 3% are wild. Another consequence of this domination is that humanity is driving evolution in many places, most obviously in domesticating crops and animals, but also through genetic modification and even by how we choose to run wildlife reserves.
Furthermore, the intricate jigsaw of life, constructed over hundreds of millions of years, has been thrown into disarray in the last 10,000 years by humans relocating species around the world. These invasive species can devastate ecosystems that have never developed defences – from rats devouring albatross chicks in their nests to snakehead fish decimating native species across the US.
However, not all scientists agree the sixth mass extinction has begun and there’s a very long way to go before we reach the 95% extinction rate seen in The Great Dying, 252m years ago. But what all researchers agree is that current biodiversity losses mean we are heading in that direction.