3.4: Habitat Loss and Fragmentation
pg. 87
Key Concepts:
4. Many human activities impact and threaten the sustainability of natural ecosystems.
- Farmland, human settlement, and highways have replace much of Southern Ontario’s
temperate forest ecosystem.
Loss and Fragmentation of Terrestrial Ecosystem
- Habitat loss is seen in the conversion of natural ecosystems into farmland and urban
development.
- Between the 19th and 20th Centuries most land had been lost to farmland and
urbanization, but more lately it has been urban sprawl and transportation.
Figure 3: When large ecosystems become fragmented, species with large home ranges
may not have enough area to survive.
- Fragmentation of ecosystems reduces ecosystem sustainability.
- On a global scale habitat loss and fragmentation are second to climate change to the
increase of habitat sustainability.
Table 1: Factors that improve the Sustainability of Habitat Fragments
Factor
Size
Poorer Option
Better Option
Explanation
Large blocks support
larger and more
populations and
communities.
Number
One large area is better
than an equal area
composed of many
smaller areas because
there is less outside
influence.
Proximity
The closer ecosystem
fragments are to each
other, the greater the
chance populations will be
able to use the entire area.
Connectedness
Interconnected areas
provide wildlife corridors
and permit migration
between larger blocks.
Integrity
Access by roads and trails
can increase pollution,
hunting, and fishing.
Figure 5: Causes of deforestation in the Amazon, 2000 – 2005
Figure 6: The former and current distribution of the loggerhead shrike.
Loss of Wetlands and Aquatic Ecosystems
- Human activity also affects aquatic ecosystems, shoreline damage from boats,
destroying natural vegetation, sediment run off, and draining of wetlands.
- There is now a desire to reverse ecosystem loss and wetlands are being re-established.
Table 2: Impact of Human Activities on Wetland and Aquatic Ecosystems
Human Activity
Replacing natural vegetation
along coastlines and
waterfronts.
Dredging to create deeper
water for boats.
Impacts on the Ecosystem
Sediment runoff from landclearing, agricultural, and
forestry operations.
Commercial Fishing.
Draining wetlands for urban
expansion and agriculture.
Evidence of Learning: Students can …
- identify some of the human activities that cause habitat loss in terrestrial ecosystems.
- describe habitat fragmentation and explain why it threatens sustainability.
- describe some of the habitat loss and fragmentation that has occurred in southern
Ontario in the last two centuries.
- identify some of the human activities that cause habitat loss in aquatic ecosystems.
Check Your Learning
Questions 1 – 7, page 90
Summary:
- Most of southern Ontario’s original natural ecosystems have been replaced by
agricultural land and urban centres.
- Habitat loss is one of the most serious threats to Earth’s ecosystems.
- Fragmentation reduces ecosystem sustainability.
- The size, proximity, connectedness, and integrity of terrestrial ecosystems will influence
their overall sustainability.
- Because of their rich soil, many wetlands have been converted into farmland.