Cornwall has varied habitats including terrestrial and marine ecosystems. Ecosystem services are defined as the gains acquired by humankind from surroundings ecosystems. Figs are keystone species in many tropical forest ecosystems. Algae are important as primary producers in aquatic ecosystems. Chemosynthetic bacteria are found in benthic marine ecosystems. It is a frequent colonizer of temperate riparian ecosystems, roadsides and waste places. The biosphere is the global sum of all ecosystems. Rainforests are the oldest ecosystems on earth. Coral reefs form some of the world's most productive ecosystems. Actual salinity varies among different marine ecosystems. This may indicate bioconcentration in aquatic ecosystems. Most arid ecosystems have inherently low productivity. These include efforts to support both ocean and forest ecosystems. Wildfires are a natural part of most terrestrial ecosystems. Other places are used for recreational purposes or conservation of native ecosystems.