The removal of natural forests and grasslands for intensive agriculture is the leading cause of the loss of wildlife ©Shutterstock/ako photography

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Destruction of forests and grasslands is biggest cause of biodiversity loss

The biggest direct driver of wildlife declines globally is the conversion of natural forests and grasslands to intensive agriculture and livestock.

This is the dramatic finding from a new paper that has looked into what is driving the unfolding biodiversity crisis. It found that land-use change caused the biggest effect over recent decades, followed by the exploitation of wildlife though fishing, logging and hunting, with pollution ranked third.

The planet is losing its wildlife at breakneck speed. Over the past four decades alone populations of mammals, birds, fish, reptiles and amphibians that scientists have monitored have fallen by an average of two-thirds.

But as we continue to put pressure on the natural world, through deforestation and over exploitation, we are threatening our own survival. This is not some existential threat that may come to pass in the distant future, but a reality we are seeing in the present. 

Knowing what is causing this rapid decline in wildlife, known more broadly as biodiversity, is essential in helping to direct how we will stop and eventually reverse it.

A new study has assessed the potential different drivers of this decline and found that land use change is the number one cause, followed by the direct exploitation of wildlife and pollution. What is perhaps most surprising is that climate change has been only the fourth largest driver of recent biodiversity loss on land. 

A mallard duck swimming in a polluted river, which is green with swirls of white and purple mixed in.

The study found that pollution is the third largest driver of biodiversity loss ©Shutterstock/iLUXimage

Professor Andy Purvis is a research lead at the Museum whose work focuses on biodiversity, and co-author of this new study published in Science Advances.

'Biodiversity is declining rapidly,' explains Andy. 'A million species of animal and plant are threatened with extinction, while ecosystems worldwide are changing away from their natural condition which means that they may be less likely to meet humanity's needs.'

'If we're going to be able to turn these recent declines round - to 'bend the curve' of biodiversity loss - we first need to know what the main causes have been.'

'This study highlights the needs to find solutions to the planetary emergency that work for nature as well as for climate.'  

The new study shows that tackling climate change on its own will not be enough to stop the catastrophic decline of the world's biodiversity, and with it our future. 

What is the biodiversity crisis?

The planet is at a major point in its 4.6-billion-year history. With carbon emissions still showing precious few signs of stopping and wildlife being squeezed into ever smaller spaces, time is tight for acting.

While a lot of attention is given to carbon emissions, there are actually two crises at play here: climate and biodiversity.

The climate crisis is currently being discussed at the COP27 climate talks happening in Egypt, where world leaders, policy makers, scientists and youth activists have gathered to build on the frameworks that were hashed out during the talks that occurred in Glasgow last year.

The causes - and solutions - to the climate crisis are relatively well known. We need to rapidly reduce our collective reliance on fossil fuels and increase the transition to renewable forms of energy, whilst simultaneously providing support to those nations currently already feeling the severe impacts of climate change.

The biodiversity crisis is the other side of the coin. As we've been releasing continuous amounts of pollution into the air, the planet's plants and animals have also been taking a hammering.

A big pile of dead fish on the deck of a boat. A man is stood in front of it, throwing a dead shark over the side of the boat.

At sea the biggest driver of biodiversity loss is overexploitation, mainly in the form of overfishing ©Shutterstock/Tara Lambourne

Each species plays an important role in maintaining the complex systems that keep the Earth functioning, including the production of clean water, the food that we eat, the air we breathe, and even our mental and physical wellbeing. As we increasingly encroach on and degrade the natural world we are slowly but surely chipping away at these vital networks.

We've known that greenhouse gasses are the leading cause of the climate crisis for decades, but figuring out what is driving the biodiversity crisis is equally important.

'We found that the most important direct driver of biodiversity change worldwide over recent decades has been land and sea-use change, with direct exploitation of plants and animals coming second,' says Andy. 'Climate change was only fourth, after pollution but ahead of invasive alien species, though it is important to note that it was ranked second in the oceans.'

'Oceans have a different ranking to land and freshwater, with direct exploitation, mostly from fishing, coming first.'

But what is occurring in the oceans may be a glimpse as to what the future will be on land. While for land-based environments climate change was only fourth biggest driver, Andy suspects that it will move up the rankings as the full effect of the climate crisis becomes more apparent over the coming years and decades. 

What can be done to tackle the biodiversity crisis?

We now know the main causes driving the dramatic decline in nature, but thankfully we also know what needs to be done to stop it.

One of the main issues is that the protection and preservation of the natural world has often taken a back seat. Perhaps this is because we have historically seen ourselves as separate from nature, while perpetuating the idea that it somehow needs to be tamed and controlled in the process of exploiting it for our more immediate needs.

But we now know that this has been to our detriment. 

The glowing embers of a tree stump in the foreground, with the burning forest in the background. The trees stand out in black against the orange glow of the fires.

Climate change has only come in as the fourth biggest driver of biodiversity loss, but as the climate crisis continues to unfold is likely to move up the rankings ©Shutterstock/My Photo Buddy

'The biodiversity crisis has to be taken seriously!' explains Andy. 'Apart from things we mine, like fossil fuels, all of our supply chains start in ecological systems. We all absolutely depend on these systems continuing to work reliably.'

'There is not yet enough recognition that economies can't grow sustainably by running nature down. And denigrating people concerned about the future of the natural world as 'eco-zealots' does nobody any good.'

Andy maintains that we need to be working towards a more holistic approach that will tackle the climate and the biodiversity crisis at the same time, to the benefit of both. This involves policies such as the 30x30 campaign, which aims to protect 30% of the land and seas by 2030.

'Climate change and biodiversity loss have been tackled largely separately, by different policies that haven't always considered the other problem,' explains Andy. 'For example, biofuels are proposed as one way to get to net zero, but the expansion of plantations into natural forest that could result would be terrible for nature.'

'That situation is improving. Last year's climate conference in Glasgow was the first time that nature had been really brought into those discussions - but there's more to be done.'

'I'd love for 'nature-positive' to get into the public consciousness as much as 'net zero' has. If future generations are going to have the same birthright we had of a liveable, supportive planet, then all parts of society will have to transition as quickly as possible to being both net zero and nature-positive.'