The variety of life on Earth

Biodiversity refers to the variety of life on Earth, including every species of bacteria, virus, plant, fungi, and animal, as well as the interactions between them and the ecosystems in which they live. The tropics are the most diverse region on Earth, hosting about 80% of the planet's terrestrial species and over 95% of its corals and mangroves.

Diverse and healthy natural ecosystems provide benefits vital for life on Earth and human wellbeing and prosperity. People rely on biodiversity and ecosystem services for sustenance, health, wellbeing and enjoyment. Human communities derive all food and many medicines and industrial products from wild and domesticated components of biological diversity. Biodiversity is also the basis for many other economic, cultural and recreational activities.

Even as our impacts on natural environments increase our knowledge of the world’s biodiversity remains limited and is highly fragmented. We haven’t yet found most species, let alone studied their biology or assessed their conservation status. While major taxonomic groups such as birds, mammals, reptiles and fish are relatively well known it is estimated that only 10% of all species have been described by science (for more on this issue see here).

The number of threatened species is a measure of how much biodiversity is impacted as a consequence of natural or anthropogenic changes to the environment. Pressures from human interactions, including habitat loss, exploitation and pollution can have substantial impacts on biodiversity. Major loss in numbers of plant or animal species can have wider effects on natural and human systems.

Tropical biodiversity is particularly susceptible to environmental changes. For all major groups assessed according to IUCN criteria, the tropics have the highest number and proportion of threatened species. Some regions have more species at risk than others, with especially high numbers under threat in tropical Asia, the Amazon and island nations.

Primary forests are forests that are still in their original condition and are largely undisturbed by human impacts. They are the most biologically diverse forests. Disturbances from natural or anthropogenic sources affect both biodiversity and the ecosystem services these forests provide. Formal recognition and protection offers the best opportunity to preserve the vital components of these systems. Changes in area of primary forest and the proportion of these forests under formal protection are additional indicators of biodiversity status.

The extent of primary forests in the tropics is decreasing rapidly with associated increased risks to biodiversity. Rates of loss remain substantial but seem to have slowed since 2000 in Central America, South America, South-East Asia and the Northern Africa/Middle East regions, although they have increased in Oceania. Technological advances based on improvements in remote sensing suggest that losses may be under reported in some regions.

Protected areas are the backbone of biodiversity conservation and environmental protection efforts worldwide. They provide refuges that protect species and habitats, sustain key natural processes and maintain ecosystem services, such as provision of clean water and air quality essential to human well-being.

Globally, the area allocated to protection has increased significantly in recent decades, with the greatest growth in the tropics where terrestrial protected area has increased by around 50% over the last 20 years. Most of this gain has been in South America which had around 26% of its land under protection in 2010. Formally protected marine area is lower globally, and the extent of area under protection in the tropics is lower than for the rest of the world. The gap is narrowing, however, and there is increasing momentum in some areas to establish protected marine reserves.

But are protected areas alone enough to maintain biodiversity?

At present, probably not. The current protected area system is unevenly distributed and not ecologically representative. Furthermore, protected areas don’t always adequately protect biodiversity, even in well-resourced areas in rich countries. This suggests that it is not enough to just set aside land or marine areas, but that these areas need to be monitored and managed far more intensively and effectively than they often are, particularly in places prone to illegal encroachment and exploitation.


In this essay, Professor Richard Corlett of the Chinese Academy of Sciences examines the potential impacts of climate change on natural and human systems in the tropics. He examines the notion that the tropics will soon have climates that have not existed anywhere on Earth for the last three million years and discusses the implications of these changes on food and water security, biodiversity and ecosystem services.