Explainer: Can climate change and biodiversity loss be tackled together?

A wildfire racing across a hillside has become emblematic of climate change. And for good reason: a quarter of the world’s natural landscapes now face longer fire seasons as a result of warming and shifts to rainfall, according to a recent landmark climate report.

But there is another global threat that worsens the risk of fire. Scientists have shown that degraded ecosystems – those that have seen their unique blend of species diluted by human disturbance – are more likely to succumb to blazes.

How global warming and biodiversity loss can conspire to drive more deadly wildfires is just one example of the numerous interlinks between these two global challenges.

As both problems escalate, scientists are racing to understand all of the ways that climate change and biodiversity loss are already compounding one another – and how the world can deploy solutions that tackle both together.

Many of the options currently on the table for tackling climate change, such as stopping deforestation and restoring natural ecosystems, would come with obvious benefits for biodiversity. However, other proposed climate solutions, such as burning crops for energy, could create large risks for the natural world.

In any case, it is clear that addressing climate change will be crucial for nature. One in 10 species is likely to face a very high risk of extinction at 2C of global warming, the upper limit of the Paris Agreement. This rises to 12% at 3C, 13% at 4C and 15% at 5C.

Though the overlap between the two challenges is becoming clearer, politicians still tackle each problem separately. The next biodiversity summit, COP15, is due to take place in China later this year after several postponements, while the next climate summit, COP27, will take place in Egypt in November.

In this Q&A, Carbon Brief explores the links between climate change and biodiversity loss – and examines whether they can be tackled as one challenge.

Both climate change and biodiversity loss are already causing severe impacts for people.

Average global temperatures have risen by 1.2C since the start of the industrial era, while CO2 in the atmosphere is at its highest level in at least two million years, according to the world’s climate authority, the Intergovernmental Panel on Climate Change (IPCC).

This has caused an increase in weather and climate extremes in every world region, the IPCC says. Just under half of the world’s population – 3.6 billion people – already live in settings “highly vulnerable to climate change”.

Human-caused climate change is already influencing the severity of extreme events, such as heatwaves, floods and wildfires. For example, the deadly heat sweeping India and Pakistan in 2022 was made 30 times more likely by climate change. In addition, extreme flooding in western Europe in 2021, which killed 220 people in Germany and Belgium, was made up to nine times more likely by climate change.

Depending on what actions humanity takes to tackle climate change, 50-75% of the global population could face “life-threatening” extreme heat by the end of the century, the IPCC says. Tropical coral reefs, which provide food or income to half a billion people, are projected to disappear if temperatures exceed 1.5C, the aspiration of the Paris Agreement.

The world’s most marginalised communities are suffering disproportionately from the impacts of climate change. This is despite the fact that most emissions come from a wealthy few. Carbon Brief analysis shows the US and Europe have together produced nearly half of all the CO2 that has been released into the atmosphere since the start of the industrial era.

The loss of biodiversity across the world is also having a major impact on people.

While many people associate the term “biodiversity” with iconic species and tropical forests, it actually covers much more than this, explains Dr Nathalie Pettorelli, a senior research fellow at the Zoological Society of London’s Institute of Zoology. She tells Carbon Brief:

The variety of living things found on Earth is crucial to human survival, explains Dr Charlie Outhwaite, a postdoctoral research associate at the Centre for Biodiversity and Environment Research at University College London. She tells Carbon Brief:

While the pace of climate change can be measured through global temperature rise and increasing greenhouse gas emissions, understanding the extent of human-caused biodiversity loss is far more complex.

This is largely because humans can affect biodiversity in myriad, far-reaching ways – for example, by destroying habitats, causing species extinctions or converting diverse ecosystems to monocultures. (Climate change also poses a major risk to biodiversity.)

And while human-caused climate change can roughly be traced back to the start of the industrial era in the 1800s, biodiversity loss has occurred since the dawn of human civilisation.

Despite these challenges, there are many signs that biodiversity loss is now at an unprecedented level as a direct result of human activities.

For example, a landmark report released in 2019 from the world’s biodiversity authority, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), found that one million animal and plant species now face extinction – more than at any other point in human history.

At least 680 vertebrate (backboned) species have already been driven to extinction since the 16th century, the report said.

A separate report from the United Nations Convention to Combat Desertification (UNCCD) released this year found that human activities have already altered 70% of the Earth’s land surface, degrading up to 40% of it. (Humans have also altered 87% of the ocean.)

Four of the nine “planetary boundaries” – limits on how humans can safely use Earth’s resources – have already been exceeded, according to the report.

The report also said that, across the world, populations of mammals, birds, amphibians, reptiles and fish decreased by an average of 68% between 1970 and 2016. In tropical central and South America, animal populations fell by 94%.

This biodiversity loss has consequences for people. An estimated $44tn – roughly half the world’s annual economic output – is currently being put at risk by the depletion of natural resources, according to the UNCCD. The loss of pollinator species specifically threatens global crops worth $577bn, IPBES says.

In addition, the loss of coastal habitats that provide a natural buffer against extreme weather events has put 100-300 million people at an increased risk of floods and hurricanes, according to IPBES.

If the unsustainable use of land continues to 2050, an additional 16m square kilometres (km2) – an area almost the size of South America – could be degraded globally, according to projections from UNCCD.

And research shows that climate change could become the largest risk facing biodiversity sometime this century. (See: How is climate change affecting biodiversity?)

Much like climate change, the global challenge of biodiversity loss is defined by large geographic and economic disparities. According to the UK Natural History Museum’s biodiversity intactness index, high levels of biodiversity loss has occurred in regions including the UK and Ireland, parts of western Europe and stretches of North America. By contrast, areas with high levels of biodiversity tend to be found in sub-Saharan Africa, South America and parts of Asia.

(And this does not consider how global north nations drove deforestation and ecosystem loss in other countries through colonialism.)

In addition, marginalised groups today play a disproportionate role in protecting the world’s biodiversity. For example, Indigenous peoples represent around 6% of the global population, yet act as stewards over 40% of intact ecosystems and protected areas.

Humans are responsible for driving both climate change and biodiversity loss.

For example, in 2019, CO2 from the fossil fuel industry accounted for 64% of all human-caused greenhouse gas emissions, according to the IPCC.

Fossil fuel extraction also poses a major threat to biodiversity, both directly through the destruction of ecosystems and indirectly by driving climate change. (Because of this, cutting back on fossil-fuel subsidies is one of the key goals of a draft deal to reverse nature loss, known as the global biodiversity framework.)

Humans’ impact on land – primarily for food production – is also a major driver of both climate change and biodiversity loss.

Food systems – a catch-all term to describe the way humans produce, process, transport and consume food – are the leading driver of biodiversity loss and also account for 29% of human-caused greenhouse gas emissions, according to UNCCD.

Animal agriculture has a particularly large climate impact. Meat and dairy specifically accounts for around 14.5% of global greenhouse gas emissions, according to the UN’s Food and Agricultural Organization (FAO).

Beef has a greater climate impact than any other food. One major reason for this is cows are ruminant animals, meaning they belch out the potent greenhouse gas methane when digesting food.

Greenhouse gas emissions per kilogram for different food groups. Adapted from Dr Hannah Ritchie/Our World in Data (2020) Data source: Poore & Nemecek (2018). Read Carbon Brief’s in-depth explainer on the climate impact of food for a full breakdown of this chart.

Another reason is that meat production requires vast areas of land to be converted for grazing or to grow animal feed. Because of this, livestock production takes up nearly 80% of global agricultural land, despite supplying less than 20% of the world’s calories.

This land conversion also makes animal agriculture a profound driver of biodiversity loss. A study published in 2018 found that the mass of animals raised for slaughter on Earth now outweighs wild mammal populations by a factor of 15-to-1.

The destruction of tropical forests for livestock production has a particularly severe climate and biodiversity impact. This is because tropical forests are carbon- and nature-rich, storing a quarter of all land carbon and supporting two-thirds of the world’s biodiversity.

In addition to cattle rearing, tropical forests are also cleared for palm oil production, logging, mining and other exploitative activities. A recent report found that, in 2021 alone, humans cut down 3.75m hectares of tropical forest – creating emissions equivalent to those caused by India’s annual fossil fuel use.

In addition to tropical forests, humans are fast degrading other carbon-rich and biodiverse ecosystems, including tropical mangroves, grasslands and underwater kelp forests.

At the root of both climate change and biodiversity loss is overconsumption of Earth’s resources, says Prof Katharine Hayhoe, a climate scientist and chief scientist at the Nature Conservancy. She tells Carbon Brief:

In addition to climate change and biodiversity loss sharing common drivers, each global challenge can worsen the other. The following two sections explore how climate change threatens biodiversity and how nature loss impedes the world’s ability to address climate change.

While humans’ impact on land remains the chief driver of biodiversity loss, climate change is playing an increasingly large – and, at times, unpredictable – role.

The IPCC’s most recent assessment of the impacts of climate change concluded that warming has already caused “substantial damages and increasing irreversible losses to land ecosystems across every region of the world”. Hayhoe tells Carbon Brief:

As temperatures increase and rainfall changes, some species are being forced to seek out new areas with climate conditions they are able to tolerate. (Species that are not able to move could face extinction.)

A scientific review of 40,000 species across the world published in 2008 found that around half are already on the move as a result of changing climate conditions.

In general, species are seeking cooler temperatures by moving towards Earth’s poles. Land animals are moving polewards at an average rate of 10 miles per decade, whereas marine species are moving at a rate of 45 miles per decade, according to the review.

This global movement of species in response to warming will have far-reaching consequences for ecosystems, explains Prof Hans-Otto Poertner, head of biosciences at the Alfred Wegener Institute (AWI) and co-chair of the IPCC’s climate impacts assessment. He tells Carbon Brief:

The reshuffling of ecosystems could be creating new risks, including increased opportunities for animals to spread their viruses, according to recent research. Increased virus sharing between animals could in turn boost the chances of a “zoonotic spillover” – the passing of harmful pathogens from animals to humans.

In addition to the threat posed by gradually increasing temperatures, biodiversity also faces risks from increases in the intensity and frequency of extreme weather events, says Dr Peter Soroye, a conservation biologist at the Wildlife Conservation Society Canada. He tells Carbon Brief:

One of the ecosystems most at risk from increases in extreme heat are tropical coral reefs.

This is because episodes of extreme ocean heat can cause “mass coral bleaching” – a phenomenon where corals expel the colourful algae that lives inside its tissue, leaving them a ghostly white. The algae acts as the primary source of food and, without it, coral slowly starves.

(Ocean ecosystems also face threats from declining levels of oxygen and acidifying waters as a result of climate change.)

The world’s largest coral reef, the Great Barrier Reef in Australia, has experienced six mass coral bleaching events since 1998. The most recent event, which took place this year, affected 91% of the reef.

The Great Barrier Reef is also the site of the first known mammal extinction caused by climate change, according to the IPCC. The IPCC says with “high confidence” that climate change played a role in the extinction of the Bramble Cay Melomys – a rat that was endemic to a vegetated coral mound at the northern tip of the Great Barrier Reef.

The coral mound, Bramble Cay, is low-lying and so vulnerable to rising sea levels and extreme weather. From 1993 to 2010, sea levels around the mound increased by 0.6cm a year – leading to increasing inundation events, which scientists believe was the most likely driver of the species’ extinction.

Climate change has also played a role in the extinction of two other species, the white ringtail possum in Australia and the golden toad in Costa Rica, according to the IPCC.

While climate change is already having a far-reaching impact on biodiversity, this effect is expected to become far larger as temperatures continue to rise.

Research published in 2018 estimated that climate change will overtake human land use to become the greatest pressure on biodiversity by 2070.

According to the IPCC, it is likely that the proportion of all species at very high risk of extinction (categorised as “critically endangered” by the IUCN Red List) will reach 9% (maximum 14%) at 1.5C, 10% (18%) at 2C, 12% (29%) at 3C, 13% (39%) at 4C and 15% (48%) at 5C, the report says.

The large uncertainty in the proportion of species facing extinction at different levels of warming reflects the fact that scientists are only just beginning to understand the impacts of climate change on biodiversity, says Dr Alex Pigot, a research fellow at UCL’s Centre for Biodiversity and Environment Research. He tells Carbon Brief:

In addition to driving species extinction, future climate change risks causing abrupt changes to entire ecosystems, says Pigot – noting that this is already occurring in some habitats, such as the Great Barrier Reef. He tells Carbon Brief:

Research published by Pigot in 2020 projected that, under a very high emissions scenario, tropical ocean ecosystems could be exposed to potentially catastrophic temperature rise by 2030, with tropical forests facing the same by 2050.

By comparison, taking action this decade in order to limit global warming to below 2C by 2100 could delay the date of exposure by up to six decades, according to the research.

In addition to climate change driving biodiversity loss, biodiversity loss also hampers the world’s ability to tackle and adapt to climate change.

When human activities release CO2, around half of it remains in the atmosphere, while the other half is absorbed by the land and ocean. These ecosystems – and the biodiversity they contain – are responsible for this carbon removal service.

Biodiversity loss reduces ecosystem functioning – which can, in turn, affect the land and ocean’s ability to absorb CO2, explains Prof Pete Smith, chair in plant and soil sciences at the University of Aberdeen. He tells Carbon Brief:

Despite humanity’s impact on land, it still functions as a net carbon sink, according to the IPCC. The land currently stores around 3.5tn tonnes of carbon, three-to-five times more than the amount stored by unextracted fossil fuels and four times more than what is currently in the atmosphere.

However, the continued degradation of land and the rising threat caused by climate change threatens to turn many land ecosystems from a carbon sink to a carbon source – whereby they emit more CO2 than they are able to absorb each year, according to the IPCC.

A study published in 2021 found that parts of the Amazon rainforest, the world’s largest single land carbon store, have already turned from a sink to source as a result of deforestation and climate change.

Research also shows that the poaching of iconic species can have an impact on an ecosystem’s ability to store carbon.

For example, a study published in 2015 found that the hunting of large mammals and birds, such as monkeys, tapirs and toucans, can reduce carbon storage in tropical forests. This is because these animals spread the seeds of large trees, an important step in their reproduction.

In addition, separate research found that the removal of white rhinos from savannah in South Africa was associated with large increases in the size of wildfires, which cause CO2 to be released from ecosystems. White rhinos are thought to be efficient fire suppressors because they graze on tall grass, which would otherwise help fires spread between trees.

As well as acting as a contributor to climate change, biodiversity loss can also impede humans’ ability to adapt to rising climate impacts.

When left intact, many ecosystems act as natural buffers against extreme weather events, such as cyclones, floods and heatwaves, says Pigot:

According to IPBES, the destruction of coastal ecosystems to date has put an additional 100-300 million people at an increased risk of floods and cyclones.

Forests also play an important role in allowing people to shade from extreme heat. A study published in 2022 concluded that, locally in all latitudes, forests aid adaptation to climate change “by reducing extreme temperatures in all seasons and times of day”.

Given the vast interlinks between climate change and biodiversity loss, calls for both challenges to be tackled as one are growing louder.

In 2021, the first joint report by the IPCC and IPBES concluded that the world must tackle climate change and biodiversity loss together if either issue is to be successfully solved.

The group of 50 scientists warned that pursuing solutions narrowly focused on climate change risked harming biodiversity and vice-versa, but that there are many options policymakers can take to tackle both problems as one.

The graphic below, taken from the IPCC-IPBES scientific outcome report, illustrates how (top) actions to tackle climate change could have positive (blue) or negative (red) impacts on biodiversity and (bottom) how actions to tackle biodiversity loss could impact climate change mitigation.

The findings show that actions to help biodiversity largely come with co-benefits for tackling climate change, says Poertner, who was co-chair of the scientific steering committee for the report. He tells Carbon Brief:

(According to the graphic, some efforts to protect biodiversity may have a small negative impact on some technologies for tackling climate change, such as limiting the available space for hydropower and BECCS. These conflicts are explained in more detail below.)

For example, the chart illustrates how conserving natural ecosystems – namely by stopping rampant deforestation and other habitat destruction – could come with benefits for both climate change and biodiversity loss.

In addition, restoring degraded ecosystems, such as carbon-rich forests and peatlands, would also bring both climate and biodiversity benefits. Pettorelli tells Carbon Brief:

“Rewilding” ecosystems to reintroduce animals in areas where they once thrived could also come with benefits for climate change mitigation, according to the findings. For example, research has previously shown that reintroducing large herbivores to forests in many parts of the globe could come with benefits for carbon storage.

The diagram also illustrates that actions focused on food systems – such as dietary change, reducing food waste and more sustainable meat production – could also help to tackle climate change and biodiversity loss together.

This reflects the fact that food production – particularly red meat rearing – is a major driver of both climate change and biodiversity loss. (See: Do climate change and biodiversity loss share common causes?)

A global switch away from meat-eating towards plant-based diets could help to deliver on climate goals while also benefiting biodiversity, Smith says:

Analysis by the IPCC shows a global switch to veganism or vegetarianism could save almost 8bn tonnes or 6bn tonnes of CO2 equivalent a year by 2050, respectively, when compared to a “business-as-usual” scenario. (By comparison, all food production currently causes around 13.7bn tonnes of CO2 equivalent a year.)

Greenhouse gas savings potential from the global adoption of various diets. Error bars show the spread of results from different studies. Data without error bars are from one study only. Adapted from IPCC (2018). Read Carbon Brief’s in-depth explaineron the climate impact of food for a full breakdown of this chart.

Freeing up land that is currently used for animals could provide new habitats, Smith says:

Another action to tackle biodiversity loss that could come with benefits for climate change mitigation is subsidy reform, according to the diagram.

Analysis published in February found that, every year, governments around the world collectively spend at least $1.8tn (£1.3tn) on subsidies that exacerbate biodiversity loss and climate change. This money, equivalent to 2% of global GDP, is being spent on support for activities such as cattle ranching, pesticide use and fossil-fuel production.

One of the targets of the global biodiversity framework is to reduce harmful subsidies by at least $500bn a year by 2030. However, some campaigners say that this should be strengthened to get rid of all harmful financing by the same date. The money saved could be redirected towards food and energy production that can support climate and biodiversity goals, they say.

As well as demonstrating how some measures could effectively tackle both climate change and biodiversity loss, the diagram (above) also illustrates how some efforts to tackle warming could pose a risk to nature.

Both large-scale tree-planting (afforestation) and bioenergy with carbon capture and storage (BECCS) are land-based climate mitigation techniques that could pose risks to biodiversity.

Afforestation differs from natural ecosystem restoration because it focuses on rapid tree growth over native habitat recovery, with some afforestation programmes relying on monoculture plantations made up of a fast-growing tree species.

BECCS is a still-emerging technique involving growing crops, burning them in a power plant to generate energy and then capturing the resulting CO2 before it is released into the air.

All scenarios for how the world can limit global temperature rise to 1.5C above pre-industrial levels rely to some degree on afforestation or BECCS.

However, scientists have raised concerns that both techniques, if poorly implemented, could risk worsening biodiversity loss further by taking up large areas of land.

For example, a study published in 2018 found that rolling out BECCS on a scale large enough to keep temperatures at 2C could pose such a large risk to land species that any benefit from reducing climate change would be cancelled out.

Both large-scale tree-planting and BECCS could pose a serious threat to biodiversity – but this could be mitigated if they are used cautiously, says Smith:

For large-scale tree-planting, there is a danger that future climate change could threaten their ability to absorb CO2, adds Pigot:

Planting a mix of tree species rather than a monoculture could help to reduce the risk from climate change – as well as provide advantages for climate and biodiversity, he adds.

The diagram also illustrates how hydropower and other forms of low-carbon energy could come with risks for biodiversity. Smith explains:

There are also fears that rapid rollout of renewable power needed for the world to limit global warming to 1.5C could also pose a risk to biodiversity.

One reason for this is, if deployed on a very large scale, wind and solar power would take up vast areas of land. And research suggests that, globally, there is overlap between biodiverse regions and areas with high wind and solar potential.

However, research published this year found that conflict between renewable power expansion and biodiversity can be largely avoided with careful planning. In a guest post for Carbon Brief, study lead author Dr Sebastian Dunnett, an ecologist at Hammersmith and Fulham Council in London, explained:

To reduce risks for biodiversity, efforts to improve energy efficiency and demand must be pursued alongside the deployment of renewable power, he added.

Despite the interlinked nature of climate change and biodiversity loss, the two problems are currently dealt with separately by the United Nations.

This began in 1992, when world leaders agreed at the Rio Earth Summit to set up the Convention on Biological Diversity (CBD) to deal with the problem of biodiversity loss and the UN Framework Convention on Climate Change (UNFCCC) to deal with global warming. (The summit also gave rise to the UN Convention to Combat Desertification.)

Each convention is governed by a Conference of the Parties (COP) – a meeting of representatives from the governments and regional bodies (such as the EU). The UNFCCC has held a COP every year since 1995, while the CBD has held a COP on even-numbered years since 1996.

The next UN climate summit, COP27, is due to be held in Egypt in November. The next UN biodiversity summit, COP15, was meant to be held in October 2020, but has been delayed four times amid the Covid-19 pandemic. The host nation China is currently seeking to delay the summit even further until 2023.

The UNFCCC has seen almost all world leaders sign the Paris Agreement, a historic pledge to keep global warming well below 2C, made in 2015. The CBD is currently working towards a similar agreement for nature, known as the post-2020 global biodiversity framework. This is after a previous agreement to halt biodiversity loss by 2020 ended in failure.

Many experts, ranging from scientists to UN leaders, have raised concerns about the two issues being addressed at separate summits.

In a recent interview with Carbon Brief, the CBD’s executive secretary Elizabeth Maruma Mrema warned against an approach of treating climate change and biodiversity loss separately, saying:

She added that there is already significant overlap between the issues discussed at climate summits and biodiversity summits:

At present, the UN considers the overlap between discussions under the CBD and the UNFCCC through something called the “Joint Liaison Group of the Three Rio Conventions”, she said.

However, she said that she believes the UN is “heading” towards holding joint summits to discuss climate change and biodiversity loss, as well as desertification. She tells Carbon Brief:

Though some experts would like to see more crossover between the CBD and the UNFCCC, there are others who think it would not be the right approach.

Li Shuo, a senior global policy adviser at Greenpeace East Asia and an observer of both climate and biodiversity talks, tells Carbon Brief:

He said that the CBD’s inability to implement meaningful measures to address biodiversity loss thus far suggests that it may not be the best vehicle for tackling the problem, adding: