Threats to biological diversity Habitat loss fragmentation THE EDGE EFFECT CORRIDORS

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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: http://ceiba.org/conservation/dry-forests/conservation-corridor/ 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: http://www.cepf.net/Documents/Final.ChocoDarienWesternEcuador.ChocoManabi.BriefingBook.pdf 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: https://natureandculture.org/nature-culture-international-helps-ecuador-establish-a-6-3-million-acre-conservation-corridor-in-amazon-rainforest/