Lecture 4 Flashcards
What was considered the most important driver of species loss globally?
Habitat loss
Pimm and Raven, 2000
What is caused by habitats being broken apart?
-A reduction in total amount of original vegetation
-Subdivision of remaining vegetation into fragments
-Introduction of new land-use to replace vegetation
Overall “landscape change”
Main changes due to habitat fragmentation
Reduced area
Reduced size
Increased isolation
Edge effect
Island biogeography
MacArthur and Wilson, 1967
Bigger islands and islands closer to the mainland tend to have more species
Species richness equilibrates where immigration and extinction curves cross
Impacts of habitat isolation
- Regular movements
- Seasonal/migratory movements
- Dispersal movements between fragments
How can edge effect be good?
Allows sunlight to hit forest floor so small plants can grow - good habitat for butterflies
Metapopulation
Many sub-populations all linked together
Wildlife corridor
Creates a connecting route between subpopulatjons in isolated habitats
Can be large e.g. the European green belt or small e.g. a tunnel under the road for animals to cross the road safely
What is the landscape perspective?
“A landscape represents a mosaic of differing quality, rather than a contrast between ‘habitat’ and ‘non-habitat’”
Bennett and Saunders, 2010
What is the landscape between fragments called?
The matrix
Drivers of habitat loss
Logging Fire Mining Agriculture (biggest cause) Trawling Urban sprawl Light pollution
What was the conclusion of the Global Forest Resources Assessment in 2015?
Forest areas have decreased since 1990 but the rate of net forest loss has been cut by 50%
Net forest gain in Central Asia and North America
Net forest loss in South America, Central Africa and Indonesia
Urban sprawl
More people now live in urban areas than rural areas. Growth of urban areas damages the surrounding habitat
Urban sprawl can be measured by light pollution
What does light pollution do?
Confused animals causing habitat loss / fragmentation
Phototaxis: many animals attracted to light (moths) whilst other nocturnal animals avoid light (bats)
Light pollution example
Lighting disrupts commuting behaviour of lesser horseshoe bats
Streetlights fragment foraging habitat as bats cannot reach woodland
