Deforestation and Fragmentation

primary cause to biodiversity loss

Habitat loss and degradation

Effects on Biodiversity globally, regionally, locally

• Globally: Most important threat to ~90% of birds,

mammals, and plants on the IUCN red list

• Regionally: Favors few characteristic species, thereby

homogenizes biodiversity.

• Locally: Declines in species richness compared to

more natural areas

Three Aspects of Habitat Degradation

1. Habitat is cleared.Habitat clearing is more consistently

damaging than fragmentation!

2. Remaining habitat is fragmented into patches.

3. New land uses are introduced

of Earth’s forest is <1km

from a forest edge

70%

analyzed how

1,673 vertebrates respond to forest edges…

85% exhibited significant responses with 46%

increasing and 39% decreasing in abundance

• has to do

  with turnover, the change in the composition.

  And in particular, the species that tended to avoid edges

  tended to be the ones that are more threatened, like this

  pangolin or this cockatoo or this tapir here

• species

  that are globally threatened are the ones that avoid these edges.

  So this tells us that, okay, maybe we've got like a

  homogenization problem, right? Because we're favoring

  these same sort of like generalist species

SLOSS: Single Large or Several Small

Several small: Multiple small patches can be spread out

to mitigate risk (like a stock portfolio)

• Single large: The Theory of Island Biogeography:

Larger and less patches isolated have more species.

– But are “habitat islands” the same as “true islands”?

Matrix

The area in between fragments.