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 geckoes, 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