GEF

Unit 5  |  The Importance of Biodiversity 109 compared with about seventy-five tree species per acre of Costa Rican forest. The rain forests of Costa Rica are home to many species. Certain regions of the Earth are considered biodiversity hotspots because they contain extraordinarily high levels of different species. Many of these species are endemic to the region, which means they are found nowhere else on Earth. Most biodiversity hotspots, such as tropical forests, are under severe threat by human activities such as agriculture, logging, and, increasingly, climate change. Another form of biodiversity is genetic diversity , which is variation within a single species. Species with large popula- tions tend to have more genetic diversity than those with small populations. If a population becomes very small or isolated, it is subject to several threats. A population with low genetic variation has less chance of withstanding disturbances such as disease or extreme drought. Inherited diseases are also a threat connected to low genetic diversity. BIODIVERSITY HOTSPOT Region of the Earth with very high levels of biological diversity, such as the Amazon basin. ENDEMIC Species that are native to a particular area and not found elsewhere. GENETIC DIVERSITY Genetic variation within a single species. ?  DID YOU KNOW Many tropical forests are considered biodiversity hotspots because they contain the highest levels of biodiversity on the planet. Brazil’s Atlantic rain forest is one example, contain- ing roughly 20,000 plant species, 1,350 vertebrate species, and millions of insect species.