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article: Deforestation in Madagascar

Biodiversity
Since its divergence from Africa over 88 million years ago, Madagascar has evolved into an incredibly biodiverse island. Including more than 13000 plants and 700 vertebrates, close to 90% of Madagascar's species are endemic and are found nowhere else in the world. However, with deforestation depleting key habitats and food resources, over 8000 species are either classified as vulnerable or endangered and some, including 15 species of lemur, have actually gone extinct. Coupled with its geographic isolation thus increasing vulnerability to destruction, deforestation will continue to impact Madagascar's flora and fauna, increasing rates of extinction.

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Lemurs are an endemic species of primates to the island of Madagascar. They act as pollinators, seed dispersers, and prey in their ecosystems. The majority of lemurs are classified as endangered due to human activities, including deforestation. This deforestation has led to different forest types in Madagascar: primary or intact forests, secondary or intermediate forests, mosaic forests, and agricultural land. The primary forests have not been deforested and are the most biodiverse. These forests have the highest abundance of lemurs. The secondary forests are somewhat degraded, but some lemur species are just as abundant in these areas. Mosaic forests are fragmented and are heavily affected by deforestation. Some species of lemurs cannot survive in these forests, while others can. Survival in these mosaic forests depends on a variety of factors, such as diet. Research suggests that omnivores and folivores can tolerate these varying habitats since their diets include a wide variety of food sources. For example, microcebus, an omnivore, has been found living in these forests and takes advantage of the abundance of insects here. However, lemurs that have specialized diets, such as frugivores, are more sensitive to habitat disturbance. These lemurs are found more often in primary forests.

Research in Masoala National Park, the largest protected forest in Madagascar, showed that there was a positive correlation between mean tree height and and lemur abundance. This explains why the primary lowland forests, which had the tallest trees and most canopy cover, had the greatest number of lemurs. Lepilemur scotterum, avahi mooreorum, and eulemur albifrons were mostly found in the greatest densities in these areas. Other species, like avahi laniger, allocebus, and microcebus, were found in equal densities in primary, secondary, and degraded forests.

A study of the Antserananomby Forest in western Madagascar in the 1960s and 70s showed it had the highest population densities for each lemur species living there. A more recent study has shown that much of the forest has been cleared for agricultural use and population densities of lemurs have declined significantly. Reduced forest size has been shown to have a direct negative effect on lemur diversity.