(5) Biodiversity and the greenhouse effect, global warming and climate change

See also environmental changes & effects on ecosystems

Global warming is causing climate change.

The diagram above describes how the Earth is kept warm by so-called 'greenhouse gases'

The 'greenhouse effect'

The Earth's temperature is the result of a balance between radiated energy received from the Sun and the energy radiated from the Earth back into space.

The incoming infrared radiation is absorbed by the land or water surface of the Earth, BUT, some of this is re-radiated at a longer wavelength of infrared radiation.

The Earth's atmospheric gases act as an insulating layer and absorbs some of the infrared heat radiation that otherwise would be re-radiated away from the Earth.

When the two are balanced, on average, the Earth maintains a steady average temperature over many years.

This increases the temperature of the Earth compared to what it would be without the atmosphere - this is one reason why organic based life exists on Earth - not to cold - Mars (little atmosphere) and our moon (no atmosphere) are much colder.

Certain gases in the atmosphere are more effective than others in absorbing the re-radiated energy - water vapor, carbon dioxide, methane, nitrous oxide and ozone all occur naturally,

but we have added other greenhouse gases like chlorofluorocarbons (CFCs) and hydrofluorocarbons (includes HCFCs and HFCs), albeit in very tiny concentrations as well as significant extra carbon dioxide in the atmosphere from fossil fuel burning - both quantities are still n the increase!

The steady rise in carbon dioxide concentration means more re-radiated infrared radiation is being absorbed by the Earth's atmosphere.

The result is that the Earth is warming up a bit more than might have been expected and the average temperature is rising.

Gas (that can have an infrared absorbing greenhouse effect)	Formula	Concentration in  atmosphere (ppm)	Contribution  (%)
Water vapour and clouds	H2O	10,000 to 50,000	36–72%
Carbon dioxide	CO2	~400	9–26%
Methane	CH4	~1.8	4–9%
Ozone	O3	2 to 8	3–7%

The % water vapour in the atmosphere varies considerably depending on the humidity and temperature - this then affects all the other percentage contributions from the other 'greenhouse gases'.

Note that the biggest greenhouse gas contributor is water vapour, but also note the very disproportionate effect of the relatively small concentration of carbon dioxide - which is rising!

Data adapted from Wikipedia page https://en.wikipedia.org/wiki/Greenhouse_gas

For more on the theory and graphs on global warming see

Absorption/emission of radiation by materials - including global warming gcse physics

and Global warming, climate change, carbon footprint gcse chemistry

 

The effects of human activity and greenhouse gases

However, although the naturally occurring greenhouse gases have been in balance for thousands of years, keeping the average temperature of the planet fairly constant, all the evidence suggests that are planet is warming up - 'global warming'.

Carbon dioxide and methane are particularly effective absorbers of the re-radiated infrared radiation

The extra carbon dioxide and methane added to the atmosphere from human activity is causing the average global temperature to rise by a small, but not insignificant amount - and the temperature rise might be accelerating - see the graph below.

Global warming graphs - all are still continuing to rise (2025 onwards)

 The Rise of CO₂ level from burning fossil fuels

 

Burning fossil fuels - graph of CO₂ produced

All these graph lines are still rising steadily in 2023.

The average carbon dioxide level in the atmosphere is now 425 ppm in 2025.

For more details see my chemistry page on global warming

 

The effects on the environment and biodiversity

Global warming is causing climate changes in weather patterns around the globe and this is having an effect on many plants and animals around the world - including us humans!

The higher global temperature is causing the seas and oceans to expand and the ice to melt e.g.  in arctic regions and glaciers around the world.

This will lead to flooding of lower level coastal land, disrupting human agriculture and the habitats of many animals.

As the temperature continues to rise weather patterns are changing with 'knock on' effects on wildlife and us!

Changes in rainfall patterns can change the distribution of plants and animals.

We humans are experiencing more exceptional weather events such as:

(i) extreme temperatures leading to drought in poorer countries,

(ii) in other places excessive rainfall and flooding destroying crops and animals and destroying animal habitats.

All these climate change effects are reducing biodiversity and disturbing season cycles of balanced populations of plants and animals.

Temperatures in the northern hemisphere are rising both on the land and in the seas.

Many species of plants and animals are becoming more widely distributed as they can now cope with living in more northern regions, this is seen in the UK. 

Changes in migration patterns are causing some animals e.g.  migrating birds, to move further north producing a wider distribution of breeding grounds.

BUT, for other plants and animals, who prefer cooler conditions, means they will tend to move north to higher temperature regions

e.g. cod in the North Sea are moving to more northern fishing grounds. 

In this case, species are becoming less widely distributed.

Most of these events and changes have a negative effect on the environment and biodiversity.

See also environmental changes and effects on ecosystems

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Key points - Summary of ideas

Based on the syllabus-specifications for students taking the AQA, Edexcel and OCR GCSE level biology examinations (~US grades 9-10).

Effects of Global Warming & Climate Change on Biodiversity

Introduction

Climate change, driven largely by global warming, is causing significant disruption to ecosystems worldwide.

Biodiversity—the variety of life on Earth, including species diversity, genetic diversity, and ecosystem diversity is being negatively affected.

Changes in temperature, weather patterns, and habitat availability threaten species survival, leading to shifts in populations, extinctions, and ecosystem imbalances.

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Key Effects on Biodiversity

1. Habitat Loss & Fragmentation

• Rising temperatures cause melting ice caps, rising sea levels, and desertification, leading to loss of natural habitats.

• Deforestation (due to climate change-related droughts and human activity) destroys ecosystems, forcing species to migrate or perish.

2. Changes in Species Distribution

• Many species are forced to migrate to cooler regions to survive, altering food chains and ecosystem stability.

• Polar species (e.g., Arctic fox, polar bear) struggle as ice melts, while tropical species face overheating risks.

3. Increased Extinction Rates

• Loss of habitat, extreme weather events, and disrupted food chains increase extinction rates.

• Species unable to adapt to rapid environmental changes die out, reducing global biodiversity.

4. Ocean Acidification and Marine Biodiversity Decline

• Increased carbon dioxide (CO₂) dissolves in oceans, lowering pH levels (ocean acidification).

• Coral bleaching occurs, killing reefs (which support 25% of marine life).

• Shellfish and plankton struggle to form shells, harming marine food chains.

5. Extreme Weather Events Disrupting Ecosystems

• More frequent hurricanes, droughts, and floods damage habitats, reducing species survival.

• Wildfires destroy large forested areas, removing shelter and food sources for animals.

6. Disrupted Reproduction and Life Cycles

• Climate change alters seasonal cycles—migratory patterns, hibernation schedules, and breeding periods.

• Food availability changes impact species like birds, which may lay eggs at the wrong time due to mismatched seasonal cues.

7. Impact on Food Chains and Ecosystem Balance

• Predators and prey experience population shifts, leading to food chain collapse.

• Loss of key species (e.g., bees, which pollinate plants) has cascading effects on ecosystems.

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What Can Be Done?

• Conservation efforts (e.g., national parks, wildlife reserves, habitat protection)

• Sustainable practices (reducing carbon emissions, reforestation, renewable energy use)

• Global cooperation (Paris Agreement, climate action policies)

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Summary of learning objectives and key words or phrases

Be able to describe the effects of climate change and global warming from the greenhouse effect and its effects on biodiversity.

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