Some consider that it is an important human responsibility to be stewards for the rest of the world's living organisms. Diversity breeds diversity. Having a diverse array of living organisms allows other organisms to take advantage of the resources provided. For example, trees provide habitat and nutrients for birds, insects, other plants and animals, fungi, and microbes. Humans have always depended on the Earth's biodiversity for food, shelter, and health.
Biodiversity also supplies indirect services to humans which are often taken for granted.
These include drinkable water, clean air, and fertile soils. The loss of populations, species, or groups of species from an ecosystem can upset its normal function and disrupt these ecological services. Recent declines in honeybee populations may result in a loss of pollination services for fruit crops and flowers Biodiversity provides medical models for research into solving human health problems. For example, researchers are looking at how seals, whales, and penguins use oxygen during deep-water dives for clues to treat people who suffer strokes, shock, and lung disease. The Earth's biodiversity contributes to the productivity of natural and agricultural systems.