3.3 Human Impacts On Biodiversity

Big ideas to keep in mind:

• Major threats to biodiversity caused by human activity include habitat loss, invasive species, pollution, overexploitation and climate change

• Conservation biology focuses on protecting ecosystems and species

On The Waterfront• More than half of the population of North America

lives on the continent’s coasts– Including the shores of the Great Lakes

• Coastal areas and shorelines are also major areas of biodiversity

• As human populations grow in these areas, more land is needed for agriculture, roads, buildings and other human activities that reduce biodiversity

• Establishing more agricultural lands may lead to more fertilizer runoff that flows into the water, creating dead zones, which are areas with low levels of oxygen that cannot support life

• The Great Lakes Water Quality Agreement pledges to reduce fertilizer runoff, improve sewage treatment and help protect ecosystems

Threats To Biodiversity• Throughout Earth’s history species have become

extinct

• Periods of mass extinction most likely occurred as a result of drastic climate change caused by volcanic eruptions or asteroid collisions

• It is believed that an asteroid impacted the Yucatan peninsula during the Cretaceous period causing a mass extinction, causing extinction of most the dinosaurs

• There is currently another period of mass extinction taking place on Earth

• Its scale is uncertain since the known number of living species (about 1.5 million) is probably only a fraction of the total number of species around

• But there are signs that species are disappearing at a dramatic rate:– about 12% of the 9900 bird species in the world are

endangered– about 300 of the 20 000 known plant species in North

America are at risk– About 37% of the known fish species have become

extinct or are at risk

1. Habitat Loss

2. Invasive Species

3. Pollution

4. Overexploitation

5. Climate Change

What is causing these threats to biodiversity?

Habitat Loss• Greatest threat to the biodiversity

• This is the factor that endangers 50% of all threatened species

• As human populations grow and develop land for communities, they destroy natural ecosystems

• If the species that inhabit those ecosystems cannot relocate or adapt to the changing conditions, they will die

• Some developments split habitats into fragments

• Habitat fragmentation alters small areas within a large region creating a patchwork of altered and original habitats

• Ex: building a road through a forest creates a barrier that may prevent species from using resources in all parts of the forest

• The smaller the fragments, the less species they can support

• Deep sea trawling is similar to deforestation, destroys coral reefs which are rich in biodiversity

Invasive Species• The next greatest threat to biodiversity

• Invasive species are non-native species that harm ecosystems where they are introduced

• They often prey on native species or outcompete them for resources

– Population size meaning resource consumption

• Humans can introduce them to new areas intentionally or accidentally as people travel

• More than 160 invasive species have entered southern Ontario and the Great Lakes region

Examples:• Accidental: seeds/spores

from plants stuck in shoes, clothes, tires; pet releases; ship ballasts;cargo containers/dunnage

• Intentional: In 1930s, kudzu plant in the southern US to help control erosion along irrigation canals… grew out of control, now as far north as Ontario

Pollution• Burning coal to produce electricity is one of the

greatest contributors to impacting biodiversity

• Coal-fired power plants emit more CO2 than vehicles

• SO2 is also produced which results in acid rain when it combines with water vapour– Acid rain damages organisms, as well as lowers the pH of

soil and water

• Also, cleaning coal results in toxins such as mercury, lead, arsenic which could enter ecosystems

Overexploitation• The unsustainable use of resources

• Humans harvest many natural resources and organisms faster than the resources can be replenished and the organisms can reproduce

• Ex: The North Atlantic cod fisheries annual catch dropped from 479 141 tons in 1988 to 12 490 tons in 1995

Climate Change• Many human activities contribute to climate change

by emitting CO2 into the atmosphere which is believed to increase global warming

• Human activities such as burning fossil fuels, clearing land by slash and burn methods, raising livestock, draining wetlands all have harmful effects on the environment

• The impacts of several human activities can combine to produce synergistic effects resulting in greater damage than the individual activities

Ex: Climate change modifies the pattern of water runoff and precipitation in NW Ontario, increasing the number of droughts. Organic matter that is normally deposited into the lakes with runoff is reduced greatly

Pollution from coal mining releases S and NO’s into the surrounding air causing acid rain. The acidification of the water decreases the amount of algae in the lake

Without algae and organic material in the lake, lake water becomes much clearer and harmful UV radiation penetrates

deeply into the water and further harms protists, plants, animals, all of which are integral parts of the food web in an

ecosystem

Conserving Biodiversity• Objective: protect ecosystems (abiotic + biotic)

• Plants and animals do not follow political boundaries, therefore it needs to be an international effort

• Convention on Biological Diversity (161 countries) employs two strategies:– ex-situ conservation: protecting species by removing

them from their natural habitats– in-situ conservation: protecting species in their natural

habitats

Protecting Species Beyond Their Habitats

• Ex-situ conservation is used when a species’ habitat is threatened or no longer exists, or the existing population of the species is very small

• The at-risk species live in zoos, gardens, reserves

• Plants: storage of seeds, cuttings of plants, living plants

• Ex: the Metro Toronto Zoo breeds and maintains a population of black-footed ferrets which no longer exist in the wild in Ontario; some have been reintroduced

Protecting Species In Their Habitats• Ex-situ conservation is considered a last resort

• In-situ conservation involves establishing protected areas, restoring habitats and adopting laws to protected threatened species

• Ex: The Lake Ontario Atlantic Salmon Restoration Program has stocked a million young salmon in three Lake Ontario streamsin an effort to bring back salmon to Lake Ontario

Take Action To Conserve Biodiversity

• Ecological Footprint: an estimate of all the land and water needed to produce the resources you consume and to absorb the wastes you produce

• The average Canadian requires ____ ha or ____ football field to maintain their lifestyle!– this is not sustainable, because if everyone on Earth had

the same ecological footprint, we would need____Earths

• You can conserve biodiversity by reducing your ecological footprint in the biosphere

• The goal of sustainable development is to develop natural resources so that they can renew themselves and be available for the future

• Sustainable development depends on the continued research and applications of ecology and conservation biology

• The challenge is to meet the needs of Earth’s population while conserving ecosystems and resources to meet the needs of the planet’s other populations as well