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What is a Biodiversity Hotspot?

What is a "Biodiversity Hotspot"? By Alan Lee

Many readers will I am sure have heard that the Tambopata is part of a World Biodiversity Hotspot. But what actually is a hotspot? The simple answer is that Biodiversity hotspots are geographic areas that contain high levels of species diversity but are threatened with extinction.

To qualify as a hotspot, a region must meet two strict criteria:
  1. It must contain at least 1,500 species of vascular plants (> 0.5 percent of the world’s total) as endemics
  2. It has to have lost at least 70 percent of its original habitat.
Three factors that usually determine hotspots
  1. The number of total species (species richness)
  2. The number of unique species (endemism)
  3. The number of species at risk (threat of extinction).
Some interesting hotspot facts:
  • 34 biodiversity hotspots have been identified.
  • They once covered 15.7 percent of the Earth’s land surface.
  • 86 % of the hotspots’ habitat has already been destroyed.
  • The intact remnants of the hotspots now cover only 2.3 % of the Earth’s land surface.
  • They contain 150,000 plant species as endemics, 50 %of the world’s total.
  • Terrestrial vertebrates endemic to the hotspots: 11,980, representing 42 percent of all terrestrial vertebrate species.
  • Reptiles and amphibians, are more prone to hotspot endemism than are the more wide-ranging mammals and birds, but the overall similarity between taxonomic groups is remarkable.
  • Overall, 22,022 terrestrial vertebrate species call the hotpots home, 77 percent of the world's total.

    DEFINING HOTSPOTS:

    Delineating hotspots is by no means an exact science. It requires that a line, that might be easily discernible or rather vague on the ground, must be drawn to represent a transition between two habitats. Less than a decade ago, the islands of eastern Melanesia, while known to be extremely endemic-rich, still held largely intact habitat. Since then, rampant logging and establishment of oil palm plantations have devastated these islands, leaving only 30 percent of their forests remaining, a situation mirroring the fate of Indonesia’s forests a decade ago.

    The problem of stemming the extinction crisis can best be framed by a question: In which areas would a given dollar contribute the most towards slowing the current rate of extinction? To accomplish this we first need to understand species’ distributions. This requires that we measure endemism: the degree to which species are found only in a given place. This can be thought of as a measure of irreplaceability. Since endemic species cannot be found anywhere else, the area where an endemic species lives is wholly irreplaceable. We also need to decide which species we should consider. Practically, vascular plants and vertebrate animals are the best candidates, because these are the only species for which we currently have sufficient data. Whether the distributions of plants and vertebrates are mirrored by terrestrial invertebrate species remains an open question, although some evidence suggests that they may be. It is less likely that the distributions of aquatic species will parallel these patterns, and so these represent an urgent research priority.

    The more threatened an area is, the more it will cost to conserve. However, because economic opportunity costs vary dramatically, there do still exist areas of relatively low cost in all hotspots. Intuitively, we want to conserve the most threatened areas first, but we also want to get the greatest return for our conservation dollar. This paradox can best be resolved by identifying areas that hold species found nowhere else and that are guaranteed to lose species if the areas are not conserved. Hotspots are not the only system devised for assessing global conservation priorities: BirdLife International has identified 218 ‘Endemic Bird Areas’ (EBAs) each of which hold two or more bird species found nowhere else. The World Wildlife Fund-U.S has derived a system called the ‘Global 200 Ecoregions’, the aim of which is to select priority Ecoregions for conservation within each of 14 terrestrial, 3 freshwater, and 4 marine habitat types. They are chosen for their species richness, endemism, taxonomic uniqueness, unusual ecological or evolutionary phenomena, and global rarity. All hotspots contain at least one Global 200 Ecoregion and all but three contain at least one EBA; 60 percent of Global 200 terrestrial Ecoregions and 78 percent of EBAs overlap with hotspots.

    HOTSPOTS IN PERIL

    Habitat destruction is a pervasive threat affecting hotspots and is already causing extinctions in many areas. Accelerating anthropogenic climate change will undoubtedly magnify the effects of habitat destruction and fragmentation. Predatory invasive species have already had a devastating impact on the island hotspots, where species evolved in the absence of animals such as cats and rats. Introduction of exotic plant species into hotspots, particularly those of Mediterranean-type vegetation, is also having massive ecosystem effects. Direct exploitation of species for food, medicine, and the pet trade is a serious threat to all hotspots, particularly in the Guinean Forests of West Africa and several Asian hotspots. Another grave concern is the severe decline of amphibians worldwide, the cause of which remains unknown. The most direct measure of this threat can be derived from assessments of conservation status of species. The IUCN Red List of Threatened Species , compiled by the Species Survival Commission of IUCN-The World Conservation Union, classifies species that have a high probability of extinction in the medium-term future as Critically Endangered, Endangered, or Vulnerable. For mammals, birds, and amphibians, the three groups of species for which assessments of distribution and conservation status have been conducted, we can measure these proportions with a high level of accuracy.

    Researchers have also found that the hotspots hold more people than expected. But the relationship between people and biodiversity is not simply one where more people lead to greater impacts on biodiversity. Human population density among hotspots varies widely, from four people per km˛ to as many as 336 people per km˛ (in Japan). Hotspots are also notable centers of violent conflict. For example, areas in Mesoamerica, the Caribbean, the Tropical Andes, the Guinean Forests of West Africa, the Eastern Afromontane rifts, the Horn of Africa, the Caucasus, the Irano-Anatolian region, the Mountains of Central Asia, Indo-Burma, Sundaland, Wallacea, the southern Philippines, and the East Melanesian Islands have all been plagued by recent violence. Most of the world's biodiversity persists in some of the world's poorest countries where conservation is not a top priority, there is a great need to develop strategies for maintaining biodiversity in human-disturbed landscapes, a discipline known as "countryside biogeography." Tropical Andes Biodiversity Hotspot The richest and most diverse region on Earth, the Tropical Andes region contains about a sixth of all plant life in less than 1 percent of the world’s land area. One of the more unique plant species is an Andean bromeliad that require 100 years to mature. The threatened yellow-eared parrot, yellow-tailed woolly monkey and spectacled bear are all endemic to the Tropical Andes. This hotspot also maintains the largest variety of amphibians in the world, with 664 distinct species. Almost 450 amphibian species are listed as threatened on the 2004 IUCN Red List. Although a quarter of its habitat still remains, the region is facing a variety of threats including mining, timber extraction, oil exploration, and narcotics plantations, which are all expanding due to the continual growth of many large cities in the region. The cloud forests are facing increased pressure from hydroelectric dams, and invasive species like the American bullfrog and grasses for cattle grazing are becoming problems as well.

    As such, we hope you enjoy your visit to Tambopata not just for the aesthetic pleasure that it provides, but also because with every tourist dollar brought into the area, this hotspot has a greater chance of survival.

    Reference: Biodiversity Hotspots





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