IPCC Assessment in depth, Part 2: How is climate change affecting land ecosystems?
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- Published on March 2nd, 2022
The threat that climate change poses to human well-being and the health of the planet is “unequivocal”, says the latest report from the United Nations’ Intergovernmental Panel on Climate Change (IPCC). In this in-depth Q&A series, Carbon Brief unpacks the key findings of the report and the developments since the IPCC’s last assessment. (Read previous section here)
How is climate change affecting land ecosystems?
Climate change has caused “substantial damages and increasing irreversible losses to land ecosystems across every region of the world, the report says.
The extent and magnitude of climate impacts on the natural world is “larger than estimated in previous [IPCC] assessments”.
Evidence suggests it is very likely that changes to the geographic ranges, physiology and morphology of land species can be attributed to climate change, the report says. Climate change is also very likely to have had an effect on animal “phenology” – the timing of key life events.
Half of all land species studied have shifted their geographic ranges in response to “regional climate changes”, the report says.
The movement of species globally is “altering the make-up” of ecosystems and “potentially” allowing the increased spread of invasive species, the report says with medium confidence.
The report says that climate change has increased wildlife diseases. Temperature rise and more brutal extreme weather events have played a 
role in the emergence of new diseases in new areas, according to experimental studies.
In countries close to the Arctic, there is evidence that climate change has helped vector-borne diseases that infect humans to expand, it adds.
Meanwhile, forest insect pests are causing greater damage in northern North America, Europe and Asia due to “warmer winters reducing mortality and longer growing seasons favouring more generations per year”.
(Read Carbon Brief’s Q&A on how climate change and biodiversity loss is changing the risk of pandemics.)
Climate change could have played a role in the extinction or near-extinction of at least three species, the report says.
It says with high confidence that climate change played a role in the extinction in the wild of the white ringtail possum in Australia and the
Bramble Cays Melomys – a rat that was endemic to a vegetated coral mound at the northern tip of the Great Barrier Reef. It adds with medium confidence that climate change drove the extinction of the cloud-forest-restricted Golden toad in Costa Rica.
A study of 976 plants and animals found that 47% had suffered local extinctions as a result of climate-induced changes, the report adds.
Since the last IPCC AR5 WG2 report was published in 2014, there has been an increasing number of biome shifts and structural changes within ecosystems, the report says.
“New studies are documenting the changes that were projected in prior reports,” the IPCC says. This includes upward shifts to alpine and boreal forests and more trees in the sub-Arctic tundra.
A combination of climate change, shifts to grazing and fire management is causing trees to encroach further into grasslands and savannahs, the report adds.
A quarter of the world’s natural land now sees longer fire seasons as a result of increases in temperature, aridity and drought, according to the findings.
Evidence shows human-caused climate change has contributed to a doubling of area burned by wildfires across the western US since the 1980s.
Forest area burned by wildfires has also increased in the Amazon, the Arctic, Australia and parts of Africa and Asia. However, these increases have not formally been linked to climate change, the report says. (Read Carbon Brief’s in-depth explainer on the links between climate change and wildfires.)
In addition, climate change is causing mass tree die-offs through its impact on droughts. It has potentially contributed to 100 cases of drought-induced tree die-off across Africa, Asia, Australia, Europe and the Americas, according to the assessment.
Despite humanity’s impact on land, it still stores more carbon than it emits each year, the report says. 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, future climate change threatens the very “fundamental aspects” of land ecosystems, the report says.
The IPCC’s “burning embers” chart below illustrates how the severity of key risks associated with land (and water) ecosystems could change
at different levels of warming.
On the chart, purple indicates a very high probability of severe impacts or risks, red signifies significant and widespread impacts or risks, yellow indicates detectable risks and white shows no detectable risks.
Black dots indicate the level of confidence in the findings, from very high (four dots) and high (three dots) to medium (two dots) and low (one dot).
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.
Insects (particularly pollinators), amphibians and flowers face the biggest extinction risks at “mid-levels of warming” (3.2C), it adds.
“Loss of species reduces the ability of an ecosystem to provide services and lowers its resilience to climate change,” the authors say.
The report notes, with medium confidence, that “more frequent and intense extreme events, superimposed on long-term climate trends, have pushed sensitive species and ecosystems towards tipping points, beyond ecological and evolutionary capacity to adapt, causing abrupt and possibly irreversible changes”.
Looking to the future, a scenario where temperature rise temporarily exceeds 1.5C for several decades before returning to below this warming level could push many species past their “physiological tolerance limit”, the report says.
“These changes may lead to collapse or transition of ecosystems to a new ecological state with a loss or altered biodiversity, including species extinctions, and loss of ecosystem services,” it adds.
At 4C of global warming, more than a third (35%) of the global land surface could witness biome shifts, the report says. This could be limited to less than 15% if temperatures are kept below 2C.
This level of warming could see large swathes of the Amazon rainforest shift to drier, less dense vegetation, further poleward shifts of boreal forests into the Arctic tundra and upslope shifts of mountain forests into alpine grasslands, the report says.
If an area is at risk of land-use change as well as climate change, the risk of biome shift can be twice or three times greater, it adds.
(For more on tipping points, see Carbon Brief’s in-depth explainer.)
A global temperature rise of 4C could also see net global wildfire frequency increase by 30%, the report says with medium confidence.
The impact of climate change on ecosystems could “substantially” increase the release of land carbon in the atmosphere, prompting “self-reinforcing” feedback loops. “The exact timing and magnitude of climate-biosphere feedbacks and potential tipping points of carbon loss are characterised by large uncertainty,” the report says.
Next: What impact is global warming having on marine life?
All sections:
- What is the IPCC report?
- How is climate change affecting land ecosystems?
- What impact is global warming having on marine life?
- How is climate change affecting the world’s water?
- What does the IPCC report say about impacts on food and agriculture?
- What risks does climate change pose to the world’s cities?
- What does the report say about public health, conflict and migration?
- How does climate change affect poverty and progress towards the sustainable development goals?
- How is the world adapting to climate change?
- What the latest IPCC report says about carbon fee and dividend
Authors:
Aruna Chandrasekhar holds an MSc in environmental change and management from the University of Oxford. She previously worked as a freelance journalist for a variety of publications, including the New York Times, Guardian, Scroll and Caravan.
Daisy Dunne holds a BSc in biology from the University of Bristol and a science journalism MA from City, University of London. She was The Independent’s climate correspondent from November 2020 to 2021. Prior to this, she was Carbon Brief’s science writer from 2017 to 2020.
Josh Gabbatiss covers climate and energy policy. Josh holds a BSc in zoology from the University of Bristol. He previously worked as science correspondent at The Independent and prior to that was a freelance journalist for a variety of scientific publications including New Scientist and BBC Earth.
