1. Threats to biological diversity Habitat loss fragmentation THE EDGE EFFECT CORRIDORS

2. What is habitat loss and fragmentation ?
Habitat loss is when a habitat is changed from one type to another
Habitat fragmentation is where habitats are divided into smaller parts

3. Why is it so important ?
Habitat loss reduces the amount of habitat available
Thought to be the most important threat to biodiversity at the moment
Fragmentation results in the pieces of habitat increasing in insularity with larger edges as well as a loss of total habitat

4. What causes habitat loss and fragmentation?
Habitat loss and fragmentation are caused primarily by humans
For example
Building
Draining wetlands
Nutrient enrichment
Grazing
Cultivation
Dredging
Stopping fire
Clearing

5. edge effects
As the habitat becomes fragmented the edge of the forest increases
The edges are different to the interior of the fragment in climate, soil environment and species composition
Each fragment of habitat is surrounded by a “matrix” which is the term used for the modified habitat

6. edge effects
The species at the edge of the habitat tend to differ from the ones in the centre of the fragment
This is seen in the vegetation present in forest fragments where
Stem density increases at the edge
Species richness increases
Shade intolerant species grow at the edge
Shade tolerant species stay in the centre
Tree mortality at patch edge

7. Edge effects – HerpEtofauna of Madagascar
On Madagascar 90% of the forests have been lost
The remaining forests persist as small isolated fragments
This increases the numbers of edges
It is suggested that these edges will affect the herpetofauna as they have quite specific physiological needs
NB Herpetofauna are the reptiles and amphibians in a habitat

8. Edge effects – HerpEtofauna of Madagascar
In one study the edge effects were found to influence the distribution of many species
The study was conducted in patches of rainforest with anthropogenic scrub in between
Some species only inhabited the interior of the forest
Some species preferred the edge of the forest
It was found that the season affected certain species affinity for the edge or interior

9. Edge effects – HerpEtofauna of Madagascar
Edge avoiders
Mantidactylus boulengeri
Interior avoiding
Mabuya elegans
Seasonal
Mantidactylus bicalcaratus
Omnipresent
Hemidactylus mercatorius
Edge avoiding reptiles and amphibians are more prone to extinction

10. island biogeography
As each fragment of habitat is surrounded by an altered habitat it is possible to look at these fragments as islands
A lot of the theory on island communities is relevant to habitat fragments
The risk of local extinction in single fragments becomes higher as the fragment is often too small to support a viable population
Re-colonisation from other fragments is possible however this depends upon the distance of the nearest fragment

11. island biogeography
A number of studies have looked at the island effect on mammals, birds and lizards in Western Australia
There are 23 preserves varying in size from 34 – 5119 hectares
The birds did not seem to be affected by this fragmentation, possibly due to their ability to re-colonise areas using shrubby growth and tree lined roads
The lizards and mammals were affected by the isolation as if their were on an oceanic island
Some of the lizards and bird had already become extinct in some of the preserves

12. Habitat destruction causes species to decline – Anuran (FROG & toads) species in Ontario Canada
70% of wetlands in southern Ontario have been destroyed
Much of this land is now used for agriculture
In a study on the anurans in the area, anuran diversity as well as density decreased in agricultural areas as well as land down stream from the agriculture
This was seen for 7 species of frog

13. Fragmentation causes species to decline – The Micro Frog
The micro frog (Microbatrachella capensis) is now on the IUCN red data list as critically endangered
This has been caused by habitat destruction
The habitat that the frog relies on is sand plain fynbos, it is unique in its composition of acidophilic plants such as ericas and proteas

14. Fragmentation causes species to decline – The Micro Frog
Over half of the sand plains fynbos on which the micro frog relies is under human settlement and only 0.013% of the fynbos type remains
One of the few remaining sites is in centre of Kenilworth race course
It has only lasted here because of the protection that the racecourse has provided
As you can see from the photo it is surrounded by human settlement
The area is only 56 hectares

15. Some species benefit
Where habitat is destroyed or fragmented some animals benefit
Grey squirrels
Rats
Foxes
Canadian Geese
Pigeons
European sparrows
House mice
But these species are often thought of as pests

16. So what can we do ?
A controversial concept is to have corridors between fragments to allow the movement of species
The idea behind a corridor is that a strip of natural habitat is allowed to remain in the unnatural matrix
It should link two fragments of habitat that are being conserved
This is meant to allow for local extinctions and re-colonisation
In practice it is not so simple

17. CONSERVATION CORRIDORS IN ECUADOR
The CIEBA foundation for Tropical Conservation is trying to unite landowners in Manabí to set up a corridor stretching along the coast:
This is just one component of the Chocó-Manabí conservation corridor proposed for the Chocó-Darién-Western Ecuador biodiversity hotspot, which runs through Colombia and Ecuador:
Nature and Culture International is working in Pastaza in the Amazon, and has an agreement to establish the 6.3 million acre conservation corridor in the rainforest: