Climate Change Affects Biodiversity

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  • by Anup Shah
  • This page last updated

The link between climate change and biodiversity has long been established. Although throughout Earth’s history the climate has always changed with ecosystems and species coming and going, rapid climate change affects ecosystems and species ability to adapt and so biodiversity loss increases.

Biodiversity and Climate Change, Convention on Biological Diversity, December, 2009

From a human perspective, the rapid climate change and accelerating biodiversity loss risks human security (e.g. a major change in the food chain upon which we depend, water sources may change, recede or disappear, medicines and other resources we rely on may be harder to obtain as the plants and forna they are derived from may reduce or disappear, etc.).

The UN’s Global Biodiversity Outlook 3, in May 2010, summarized some concerns that climate change will have on ecosystems:

Climate change is already having an impact on biodiversity, and is projected to become a progressively more significant threat in the coming decades. Loss of Arctic sea ice threatens biodiversity across an entire biome and beyond. The related pressure of ocean acidification, resulting from higher concentrations of carbon dioxide in the atmosphere, is also already being observed.

Ecosystems are already showing negative impacts under current levels of climate change … which is modest compared to future projected changes…. In addition to warming temperatures, more frequent extreme weather events and changing patterns of rainfall and drought can be expected to have significant impacts on biodiversity.

Secretariat of the Convention on Biological Diversity (2010), Global Biodiversity Outlook 3, May, 2010, p.56

Some species may benefit from climate change (including, from a human perspective, an increases in diseases and pests) but the rapid nature of the change suggests that most species will not find it as beneficial as most will not be able to adapt.

On this page:

  1. Climate change impacts on biodiversity in the Arctic
  2. Climate change means ocean change
  3. Increasing ocean acidification
  4. Increasing ocean stratification
  5. Increasing oceanic dead zones
  6. Coral reefs threatened by climate change
  7. Lizards threatened by climate change
  8. Other examples

Climate change impacts on biodiversity in the Arctic

The Arctic, Antarctic and high latitudes have had the highest rates of warming, and this trend is projected to continue, as the above-mentioned Global Biodiversity Outlook 3 notes (p. 56).

In the Arctic, it is not just a reduction in the extent of sea ice, but its thickness and age. Less ice means less reflective surface meaning more rapid melting. The rapid reduction exceeds even scientific forecasts and is discussed further on this site’s climate change introduction.

The polar bear depends on sea ice. (Image source)

In terms of biodiversity, the prospect of ice-free summers in the Arctic Ocean implies the loss of an entire biome, the Global Biodiversity Outlook notes (p. 57).

In addition, Whole species assemblages are adapted to life on top of or under ice — from the algae that grow on the underside of multi-year ice, forming up to 25% of the Arctic Ocean’s primary production, to the invertebrates, birds, fish and marine mammals further up the food chain. The iconic polar bear at the top of that food chain is therefore not the only species at risk even though it may get more media attention.

Note, the ice in the Arctic does thaw and refreeze each year, but it is that pattern which has changed a lot in recent years as shown by this graph:

The extent of floating sea ice in the Arctic Ocean, as measured at its annual minimum in September, showed a steady decline between 1980 and 2009.Source: National Snow and Ice Data Center, graph compiled by Secretariat of the Convention on Biological Diversity (2010) Global Biodiversity Outlook 3, May 2010

It is also important to note that loss of sea ice has implications on biodiversity beyond the Arctic, as the Global Biodiversity Outlook report also summarizes:

  • Bright white ice reflects sunlight.
  • When it is replaced by darker water, the ocean and the air heat much faster, a feedback that accelerates ice melt and heating of surface air inland, with resultant loss of tundra.
  • Less sea ice leads to changes in seawater temperature and salinity, leading to changes in primary productivity and species composition of plankton and fish, as well as large-scale changes in ocean circulation, affecting biodiversity well beyond the Arctic.
Secretariat of the Convention on Biological Diversity (2010), Global Biodiversity Outlook 3, May, 2010, p.57

(This site’s intro to climate change and Arctic geopolitics has more about the impact to the Arctic.)

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Climate change means ocean change

When talking about the impacts of climate change, we mostly hear about changes to land and the planet’s surface or atmosphere. However, most of the warming is going into the oceans where a lot of ecosystem changes are also occurring:

Over 93% of global warming is going into the oceans
Source: John Cook, Infographic on where global warming is going,, January 20, 2011 (further notes on the source data used)

As John Cook, creator of the graphic above says (see above link), Just as it takes time for a cup of coffee to release heat into the air, so to it takes time for the ocean to release its heat into the atmosphere..

Indeed, as this chart also shows, the warming in the oceans has been occurring for quite some time:

Source: John Bruno, It’s not climate change, it’s ocean change!, Climate Shifts, July 12, 2010

The implications of this is further explained with Inter Press Service’s freezer analogy: The world’s northern freezer is on rapid defrost as large volumes of warm water are pouring into the Arctic Ocean, speeding the melt of sea ice.

One of John Bruno’s colleagues, Ove Hoegh-Guldberg, talks about the impact climate change will have on ocean ecosystems. A summary of the video here says that

Ove Hoegh-Guldberg NCSE talk on climate change impacts on ocean ecosystems, Climate Shifts, January 21, 2011.

Rapidly rising greenhouse gas concentrations are driving ocean systems toward conditions not seen for millions of years, with an associated risk of fundamental and irreversible ecological transformation. Changes in biological function in the ocean caused by anthropogenic climate change go far beyond death, extinctions and habitat loss: fundamental processes are being altered, community assemblages are being reorganized and ecological surprises are likely.

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Increasing ocean acidification

Ocean Acidification; consumption of carbonate ions impede calcification. Source: Pacific Marine Environment Laboratory, NOAA

Although it has gained less mainstream media attention, the effects of increasing greenhouse emissions — in particular carbon dioxide — on the oceans may well be significant.

NOAA Ocean Acidification Demonstration, National Oceanic and Atmospheric Administration, February 26, 2010

As explained by the US agency, the National Oceanic and Atmospheric Administration (NOAA), the basic chemistry of ocean acidification is well understood.

These are the 3 main concepts:

  1. More CO2 in the atmosphere means more CO2 in the ocean;
  2. Atmospheric CO2 is dissolved in the ocean, which becomes more acidic; and
  3. The resulting changes in the chemistry of the oceans disrupts the ability of plants and animals in the sea to make shells and skeletons of calcium carbonate, while dissolving shells already formed.
Short overview of ocean acidification: Ocean Acidification, ABC World News Webcast, June 7, 2008

Scientists have found that oceans are able to absorb some of the excess CO2 released by human activity. This has helped keep the planet cooler than it otherwise could have been had these gases remained in the atmosphere.

However, the additional excess CO2 being absorbed is also resulting in the acidification of the oceans: When CO2 reacts with water it produces a weak acid called carbonic acid, changing the sea water chemistry. As the Global Biodiversity Outlook report explains, the water is some 30% more acidic than pre-industrial times, depleting carbonate ions — the building blocks for many marine organisms.

In addition, concentrations of carbonate ions are now lower than at any time during the last 800,000 years. The impacts on ocean biological diversity and ecosystem functioning will likely be severe, though the precise timing and distribution of these impacts are uncertain. (See p. 58 of the report.)

Although millions of years ago CO2 levels were higher, today’s change is occurring rapidly, giving many marine organisms too little time to adapt. Some marine creatures are growing thinner shells or skeletons, for example. Some of these creatures play a crucial role in the food chain, and in ecosystem biodiversity.

Clay animation by school children: The other CO2 problem, March 23, 2009 (commissioned by EPOCA)

Some species may benefit from the extra carbon dioxide, and a few years ago scientists and organizations, such as the European Project on OCean Acidification, formed to try to understand and assess the impacts further.

One example of recent findings is a tiny sand grain-sized plankton responsible for the sequestration of 25–50% of the carbon the oceans absorb is affected by increasing ocean acidification. This tiny plankton plays a major role in keeping atmospheric carbon dioxide (CO2) concentrations at much lower levels than they would be otherwise so large effects on them could be quite serious.

Other related problems reported by the Inter Press Service include more oceanic dead zones (areas where there is too little oxygen in the sea to support life) and the decline of important coastal plants and forests, such as mangrove forests that play an important role in carbon absorption. This is on top of the already declining ocean biodiversity that has been happening for a few decades, now.

Scientists now believe that ocean acidification is unparalleled in the last 300 million years, raising the possibility that we are entering an unknown territory of marine ecosystem change.

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Increasing ocean stratification

As climate change warms the oceans (even just an increase of about 0.2C per decade, on average), the warmer water (which is lighter) tends to stay on top of what is then a layer of colder water.

Tiny phytoplankton: the foundation of the oceanic food chain. Source: NOAA MESA Project.
Phytoplankton Bloom in the North Atlantic. Source: NASA Earth Observatory.

This affects tiny drifting marine organisms known as phytoplankton. Though small, Phytoplankton are a critical part of our planetary life support system. They produce half of the oxygen we breathe, draw down surface CO2, and ultimately support all of our fisheries, says Boris Worm of Canada’s Dalhousie University and one of the world’s leading experts on the global oceans (quoted by Inter Press Service — IPS.)

In the same news report, IPS explains that phytoplankton can only live in the top 100 or 200 meters of water, but if it is getting warmer, they eventually run out of nutrients to feed on unless the cold, deeper waters mix with those near the surface.

Ocean stratification has been widely observed in the past decade and is occurring in more and larger areas of the world’s oceans, IPS also adds.

Researchers have found a direct correlation between rising sea surface temperatures and the decline in phytoplankton growth around the world.

As NASA summarizes, stratification cuts down the amount of carbon the ocean can take up.

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Increasing oceanic dead zones

The past half-century has seen an explosive growth in aquatic dead zones, areas too low in dissolved oxygen to support life.

Aquatic dead zones often occur near high human population density. Source (including larger image): NASA Earth Observatory.

Fertilizer and sewage run-off cause huge growth of plankton. However, these then quickly die and are consumed by bacteria that deplete waters of oxygen. For example, the Gulf of Mexico has a 22,000 square kilometer dead zone every spring due to run-off from the Mississippi River.

Professor Robert Diaz, of the Virginia Institute of Marine Science, explains ocean dead zones further in this short video:

What are dead zones?, IPSO, October 2, 2013

There is also a linkage with climate change:

Ocean stratification, where warm water sits firmly on top of cold, nutrient-rich water, also creates dead zones and lowers the overall productivity of the oceans.… Such dead zones were rare 40 years ago but now number several hundred. Without urgent action, climate change will continue to warm oceans, increasing stratification and producing larger and more dead zones with a major impact on future fisheries, a 2009 study in Nature Geoscience warned.

It will take a thousand years for the oceans to cool down, so it is imperative to pull the emergency brake on global warming emissions, the study concluded.

Stephen Leahy, Ocean Losing Its Green, Inter Press Service, July 31, 2010

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Coral reefs threatened by climate change

Around the world, coral reefs have been dying largely due to climate change.

Coral bleaching results in white, dead-looking, coral. Healthy coral is very colorful and rich with marine life.

At the beginning of September, 2009, the Australian agency looking after the Great Barrier Reef released an outlook report warning the Great Barrier Reef is in trouble.

But it is not just the Great Barrier Reef at risk. All of them are at risk, says Charlie Veron, an Australian marine biologist who is widely regarded as the world’s foremost expert on coral reefs.

The future is horrific, he says. There is no hope of reefs surviving to even mid-century in any form that we now recognize. If, and when, they go, they will take with them about one-third of the world’s marine biodiversity. Then there is a domino effect, as reefs fail so will other ecosystems. This is the path of a mass extinction event, when most life, especially tropical marine life, goes extinct.

Coral reefs provide many ecosystem services to humans as well, for free. This site’s page on coral reefs goes into these issues in more depth.

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Lizards threatened by climate change

(Image credit: Iker Cortabarria)

What the BBC described as a global-scale study published in the journal Science found that climate change could wipe out 20% of the world's lizard species by 2080.

Global projection models used by the scientists suggested that lizards have already crossed a threshold for extinctions caused by climate change.

The fear of lowland species moving to higher elevations has long been predicted as an effect of climate change. This has been observed with lizard populations too, as the leader of the research team told the BBC: We are actually seeing lowland species moving upward in elevation, slowly driving upland species extinct, and if the upland species can’t evolve fast enough then they’re going to continue to go extinct.

Why are lizards so sensitive to climate change? The BBC summarizes:

Lizards, the researchers say, are far more susceptible to climate-warming extinction than previously thought. Many species live right at the edge of their thermal limits.

Rising temperatures, they explained, leave lizards unable to spend sufficient time foraging for food, as they have to rest and regulate their body temperature.

Victoria Gill, Climate change link to lizard extinction, BBC, May 14, 2010

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Other examples

The above areas of biodiversity affected is by no means exhaustive. Other areas affected by climate change include terrestrial animals, and forests, water sources and related ecologies, and so on. For more information on those areas, see this site’s sections on

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Author and Page Information

  • by Anup Shah
  • Created:
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Document revision history

Added small video explaining ocean dead zones
Added a small note that ocean acidification looks to be worse in 300 million years
Added a section on climate change’s impacts on ocean ecosystems
Added additional notes and multimedia on ocean acidification. Also added a section on increasing ocean stratification and a section on growing aquatic dead zones.
Completely rewrote this page, as it had not been updated since February 2000. Introduced the impact of climate change on biodiversity especially in the arctic and the oceans

Alternatives for broken links

Sometimes links to other sites may break beyond my control. Where possible, alternative links are provided to backups or reposted versions here.