eachch species has very spececil habitatt requirements. once you destroy those, you dedestroy the species. >> we are cutting down our rain forests s at an alarming rate. we are overfrfishing in ththe ocean, we are consuming natural resources at an unsustainable rate. the earth's surface has already been altered by humans. three-quarters will be altered in the next 30 years. pollution from farms, pesticides, and fertilizer runoff as causing dead zones in lakes and sees. 80 percent of the world's fisheries are depleted, over exploited, or in a state of collapse. one-third of all coral species are at risk of extinction. we are definitely a big past on earth. destroying some ecosystems. >> climate change will make an already bad situation worse and could become a factor most responsible for species' extinction in the next century. based pcpcs3030% of land- arare at risk from extinctctiony century's end. >> nobody knows what thahat is going to mean. clearly, a tremendous problems with food, tremendouous problems with water, tremendous death of