Biodiversity is the variety of life including animals, plants, fungi, protists, bacteria found in the ecosystem. Tropical islands such as those in the Caribbean, are experiencing decreased biodiversity. There are many factors that can affect the numbers and varieties of organisms in an area. The greater the species richness, the healthier the planet will remain. There are estimates that approximately 30% of current species will become extinct by 2050. Islands are most vulnerable to factors affecting biodiversity because these are smaller areas, they are separate from the mainland and pressures can have a greater affect in these isolated locations. The introduction of exotic species can wreak havoc on an island. A non-native species can outcompete the indigenous species for food and space and can cause its extinction. It might not have any predators to keep its numbers in check. Habitat destruction can affect biodiversity by deforestation to clear land for farming. Habitat destruction means less areas for species to nest, thrive, hunt and ultimately, might mean their demise. In tropical rainforests, increased rates of extinction are being driven by human consumption of goods taken from the rainforest, including lumber, foods and other organic products. Cutting down rainforests, to provide farmlands and orchards is leading to loss of species like songbirds, rare plants and other animals. Biodiversity is necessary for the health of the planet so that water can be purified, air can be replenished, excess carbon dioxide can be fixed by plants into glucose, rather than remaining in the air adding to global warming.