Islands are home to some 600 million people—one-tenth of the world's population. Many islanders are endowed with unique cultures and derive much of their economic, environmental and cultural well-being directly or indirectly from the rich natural resources in their immediate environment. Islands harbour numerous discrete ecosystems, from mountain forests to wetlands and beyond, that provide food, fresh water, wood, fibre, medicines, fuel, tools and other important raw materials, in addition to aesthetic, spiritual, educational and recreational values, that support island livelihoods, economies and cultures. Island ecosystems also contribute to the maintenance of ecosystem functions: they provide defence against natural disasters, support nutrient cycling, and soil and sand formation; and they contribute to the regulation of climate and diseases.

While much the same can be said of biodiversity in other settings, the components of biodiversity and the ecosystem services they provide is all the more critical on islands. Island economies, particularly those of Small Island Developing States (SIDS), are among the most vulnerable of the developing countries, considering the relative lack of economic alternatives available and such factors as:

· Small populations and economies
· Weak institutional capacity in both the public and the private sector
· Remoteness from international markets
· Susceptibility to natural disasters and climate change (including in particular sea-level rise from climate change)
· Fragility of land and marine ecosystems
· High cost of transportation
· Limited diversification in production and exports
· Dependence on international markets, export concentration, and income volatility
· Vulnerability to exogenous economic shocks.

These challenges and vulnerabilities prompted Agenda 21 (chapter 17, section G; 1992), followed by the Barbados Programme of Action (1994) and the Plan of Implementation of the World Summit on Sustainable Development (2002), to call small island developing States and islands supporting small communities “a special case both for environment and development.”

For example, biodiversity is a crucial component of food security in many small, isolated islands, especially SIDS. Small islands comprise a high proportion of marine and coastal areas, which are important sources of income. The continental shelves and coastal ecosystems of many SIDS are of major economic significance for settlement, subsistence and commercial agriculture, fisheries, and tourism. Coastal ecosystems also fulfill many ecological roles, ranging from shoreline protection to buffer zones from land-based activities and pollution, to feeding, breeding, and nursery grounds to many marine species. Coral reefs provide an estimated US$ 375 billion per year in goods and services to the world. This includes support for marine fisheries, which provide the principal protein source for many island populations, especially amongst SIDS.

Yet island biodiversity is not only of vital importance to island dwellers. Islands are repositories of genetic information whose present-day biodiversity stands as a record of millions of years of evolution. This biodiversity has an inherent value to humankind the world over.