Habitat Loss - Conservation Biology - Lecture Slides, Slides of Biology

Download Habitat Loss - Conservation Biology - Lecture Slides and more Slides Biology in PDF only on Docsity!  Habitat loss is when a habitat is changed from one type to another  Habitat fragmentation is where habitats are divided into smaller parts What Is Habitat Loss And Fragmentation ? Docsity.com  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 WHY IS IT SO IMPORTANT ? Docsity.com  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 1 Docsity.com  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 herpatofauna as they have quite specific physiological needs EDGE EFFECTS – HERPATOFAUNA OF MADAGASCAR 2 Docsity.com  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 – HERPATOFAUNA OF MADAGASCAR 2 Docsity.com  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 ISLAND BIOGEOGRAPHY 3 Docsity.com  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 HABITAT DESTRUCTION CAUSES SPECIES TO DECLINE – ANURAN SPECIES IN ONTARIO CANADA 5 Docsity.com  The micro frog (Microbatrachella capensis) is now on the IUCN red data list as critically endangered 6  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 7 FRAGMENTATION CAUSES SPECIES TO DECLINE – THE MICRO FROG Docsity.com  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 SO WHAT CAN WE DO ? Docsity.com  Fahrig and Merriam (1985) 8 tested a model that compared the age structure and population size of patches of habitat that were linked or not  They then applied the model to the white footed mouse (Peromyscus leucopus)  The white footed mouse lives in patchy forests and doesn’t like open areas  They applied the model to populations of mice that were isolated or linked to another population by a corridor  They found that isolated populations had a lower growth rate FOR CONSERVATION CORRIDORS Docsity.com  A study by Aars and Ims (1999) 9 focused on voles  They looked at population sizes and the genetics of the population  The voles had the same population size with or without the corridor  The corridor enhanced the movement of female voles from one population to the other  The corridor did not affect the movement of males from one population to the other  This small increase in movement by the female voles could enhance genetic diversity within the fragmented populations FOR CONSERVATION CORRIDORS Docsity.com