Impacts of Climate Change on Ecosystems (DP IB Environmental Systems & Societies (ESS))

Impacts of Climate Change on Ecosystems

• Climate change:

  • Impacts ecosystems on various scales, from local to global

  • Affects the resilience of ecosystems

  • Leads to biome shifts

Local impacts

Coral bleaching

• Cause:

  • Increased sea temperatures cause corals to expel the algae (zooxanthellae) living in their tissues

  • Without these algae, corals lose their colour (giving them a white appearance)

  • They also lose their main food source (the algae perform photosynthesis, producing organic compounds that the corals use as a primary energy source)

  • This leads to bleaching and eventually coral death

• Effects:

  • Loss of biodiversity as fish and other marine species lose their habitat

  • Decline in fish populations in reef ecosystems

• Example:

  • The Great Barrier Reef in Australia has experienced significant coral bleaching events

Desertification

• Cause:

  • Prolonged droughts and higher temperatures

  • Unsustainable land practices like deforestation and overgrazing

• Effects:

  • Loss of arable land and vegetation, leading to soil erosion

  • Reduced agricultural productivity

  • Displacement of communities

• Example:

  • The Sahel region in Africa is facing severe desertification, affecting local livelihoods that rely on agriculture

Global impacts

Changes to ocean circulation

• Cause:

  • Melting ice caps and glaciers increase the freshwater input into oceans

  • This disrupts normal currents and circulation patterns

• Effects:

  • Altered weather patterns

  • Changes in marine and coastal ecosystems

  • Changes in fish migration and distribution affecting fisheries

• Example:

  • Slowing down of Atlantic Meridional Overturning Circulation (AMOC), which includes the Gulf Stream

  • This is leading to colder winters in Europe and warmer temperatures in the Arctic

Sea-level rise

• Cause:

  • Melting ice caps and glaciers

  • Thermal expansion of seawater due to higher temperatures

• Effects:

  • Coastal flooding and erosion, impacting ecosystems like mangroves and salt marshes

  • Loss of habitats for species in these biodiverse ecosystems

• Example:

  • The Maldives is at risk of becoming uninhabitable due to rising sea levels

Regional impacts on natural productivity

Increased productivity

• Northern regions:

  • Warmer temperatures can extend the growing season and increase vegetation

  • Expansion of suitable areas for agriculture and forestry

  • For example, in parts of Canada and Russia, agriculture is expanding northward and growing seasons are longer due to warmer conditions

Decreased productivity

• Tropical regions:

  • Higher temperatures and unpredictable rainfall can harm crops

  • For instance, shifting monsoon patterns in Southeast Asia are threatening rice yields

Factors affecting ecosystem resilience

Biodiversity

• Climate change can reduce resilience by decreasing biodiversity

• High biodiversity:

  • Increases resilience by providing a variety of species that can adapt to changes

  • For example, tropical rainforests have high biodiversity, helping them recover from disturbances

• Low biodiversity:

  • Decreases resilience, making ecosystems more vulnerable

  • For example, monoculture farms are less resilient to pests and diseases

• Impact of climate change:

  • Climate change can lead to habitat loss, altered food webs and extreme weather events

  • All of these can reduce biodiversity

    • For example, coral bleaching due to increased sea temperatures reduces the variety of species in coral reefs

    • This can reduce the resilience of coral reefs to other stressors, like ocean acidification or increased tropical storms

Habitat fragmentation

• Climate change can also reduce resilience by causing habitat fragmentation

• Connected habitats:

  • Enable species to migrate and adapt to changes

• Fragmented habitats:

  • Isolate species and split populations, reducing their ability to adapt

• Impact of climate change:

  • Rising temperatures and changing precipitation patterns can shift habitats, leading to fragmented landscapes

  • Climate change can fragment habitats in various ways:

    • Increased desertification: expanding deserts can divide ecosystems, making it harder for species to find resources and migrate

    • Increased rates of forest fires: more frequent and intense fires can break up forest ecosystems, isolating populations and reducing biodiversity

    • Melting polar ice caps: loss of ice habitats can fragment the habitats of polar species like polar bears and penguins, affecting their ability to hunt and reproduce

    • Species in mountainous regions might be forced to move to higher altitudes, creating isolated populations

• These changes reduce the resilience of ecosystems by isolating species and limiting their ability to adapt to new conditions

Biome shifts

• Climate change can result in biome shifts

  • This is where ecosystems change in location or type due to altered climatic conditions

• Cause:

  • Changes in temperature, precipitation and extreme weather events

• Effects:

  • Movement of biomes:

    • Biomes, such as forests, grasslands and tundra, may shift towards the poles or higher altitudes as species (including plants) shift ranges to find suitable climates

    • For example, in North America, temperate forests are moving northward, slowly replacing boreal forests

    • As species move to new areas or experience changes in their habitats, they may face new competition, predation, or disease

  • Transformation of existing biomes:

    • Current biomes may change in structure and composition

    • For example, the Arctic tundra is transforming into shrubland as warmer temperatures allow shrubs to grow

  • Loss of unique biomes:

    • Some biomes may disappear if conditions become unsuitable for the species that inhabit them

    • For example, alpine regions may lose their unique flora and fauna as temperatures rise and snow cover decreases

    • This can lead to declines in population numbers and even extinction in some cases