Ecosystem Services concern the free benefits humans derive from the natural world. Scientists have recently begun to evaluate their relative financial value to humankind, especially as ecosystems are modified and degrade and can no longer provide their original functions.
Pollination:
Intact ecosystems provide habitats for pollinators; the “work-horses” that we depend upon on for the fertilisation of crops such as: apples, potatoes, plums, tomatoes, melons, blueberries, squash, alfalfa and clover.
Bees and butterflies are not the only pollinators that humans are dependent upon; over 100,000 species of animals ranging from hummingbirds, to geckos, beetles and bats provide crucial pollination services to flowering plants and in turn humans.
A study by Cornell University in 2012 attributed insect pollination as contributing $29 billion annually to the U.S. farm income.
http://www.news.cornell.edu/stories/May12/Pollinators.html
http://conservationbytes.com/2008/09/22/pollination-worth-153-billion-euros-per-year/
http://www.esa.org/ecoservices/comm/body.comm.fact.poll.html