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Threats to Biodiversity

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Sarah Digan

on 21 September 2017

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Transcript of Threats to Biodiversity

Threats to Biodiversity:

Habitat Destruction
Global Climate Change

Habitat Destruction
cause of the loss of biological diversity is not direct human exploitation but the habitat destruction resulting from the
expansion of human populations and human activities
Habitat loss reduces the amount of habitat available.

Habitat Fragmentation
What is Biodiversity?
Ecological Footprint
Causing Habitat Destruction
 Buildings, Streets
 Land Clearing
 Soil Degradation
 Draining wetlands
 Nutrient enrichment
 Grazing
 Cultivation
 Dredging
 Stopping fire
Habitat Loss in Australia
The percentage of threatened freshwater and terrestrial species in each subcatchment affected by (a) habitat loss, (b) introduced species, (c) inappropriate fire regimes, (d) disease, (e) pollution, (f) overexploitation, (g) native species interactions and (h) natural causes; the distribution of threatened species richness is shown in (i)
The ecological footprints (in hectares) of countries around the world
Human Population Growth and its impact
Three Ways Humans Dominate the Global Ecosystem
Land Surface
(resource needs, land use); half of the Earth's ice-free land surface already transformed

Nitrogen Cycle
(cultivating nitrogen-fixing crops, using nitrogen fertilizers and burning fossil fuels, release more nitrogen into terrestrial systems than is added by natural processes.

Use of fossil fuels and deforestation

Global Climate Change
Evidence for Global Warming:
1. Increased temperatures and incidence of heat waves
2. Melting of glaciers and polar ice
3. Rising sea levels
4. Earlier spring activity
5. Shifts in species ranges
6. Population declines

Habitat Degradation
Pesticide Pollution
Water Pollution
Air Pollution
Pesticide Pollution
: toxic chemicals (pesticides) become concentrated as they ascend the food chain ('Silent Spring' by Rachel Carson, 1962, DDT)
Impact (
) of any human population on the environment
P =
number of people
A =
average income
T =
level of technology
Toronto in Canada has an area of 630 km2 but each citizen requires the environmental services of 7.7 ha (0.077 km2) to provide water, food, and waste disposal sites.
Toronto has a population of 2.4 million people.
Toronto requires an ecological footprint of 185,000 km2.
Atlas of Global Conservation
Habitat Loss in Australia
Ecological footprints can be increased by:
great reliance on fossil fuels
increased use of technology and, therefore, energy
high levels of imported resources
large per capita production of carbon waste
a meat-rich diet
per capita food consumption

mean food production of local arable land
Threats to Coral Reefs:
(predation, rising sea tempeartures, tides and waves)
(collection, fishing; sewage discharge, dredging; run-off such as oil, insecticides, nutrients, sediments, etc.)
Habitat area is severely reduced by fragmentation and edge effects.

Edge effects, illustrated here in grey: changes in light, humidity, temperature, and wind that may be less favorable for many species living there.

Summary: Edge Effect
1. Fragments have a great amount of edge per area of habitat (and thus a greater exposure to the edge effect).
2. The centre of each habitat fragment is closer to an edge.
3. A formerly continuous habitat hosting large populations is divided into pieces, with smaller populations.
Interspecies Interaction
Increased vulnerability of the fragment to invasion by exotic and native pest species.

The forest edge represents a high-energy, high-nutrient, disturbed environment in which many pest species of plants and animals can increase in number.

Microclimate changes
Sunlight is absorbed and reflected by the layers of leaves in forest communities. In mature forests, often less than 1% of the light energy may reach the forest floor (keeping it cool and moist, reducing air movement).

When the forest is fragmented, these effects are removed.

In studies of Amazon forests, tree mortaility could be detected within 100 to 300 m of forest edges.
Increased incidence of fire
Increased wind, lower humidity and higher temperatures make fires more likely.
Population Effects
Water pollution not only damages biodiversity but also harms the health of people who use water.
used by people or given to domestic animals enter the aquatic environment through inadequately treated sewage. The medicines, especially hormones, can have an adverse effect on the physiology, behavior and reproduction of fish and other animals that ingest these biologically active chemicals.
: initiated by human sewage, agricultural fertilizers, detergents and industrial processes as these release large amounts of nitrates and phosphates. [The key to stopping this is to reduce the release of excess nutrients through improved sewage treatment and better farming practises as well as the establishment of buffer zones between fields and waterways.]
Dead zone
: consisting of only those species tolerant of polluted water and low oxygen levels (e.g. algae).
Plastic pollution
: a huge problem in the marine environment. Marine animals such as seabirds and turtles eat plastic trash by mistake and eventually die because their stomachs are full of non-nutrious, indigestible items. [worst: plastic bags]
Eroding sediments
: from logged or farmed hillsides, diminishes the rate of photosynthesis due to sediment cover, turbidity. [especially harmful to corals]
Water Pollution
Water pollution severely damages aquatic ecosystems.
Pesticides, herbicides, oil products, heavy metals (such as mercury, lead and zinc), detergents, toxic chemicals such as polychlorinated biphenyls and industrial wastes directly kill organisms.
Air Pollution
Acid Rain
Ozone Production and Nitrogen Deposition
Toxic Metals
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