A new United Nations report, a massive undertaking by 1,500 scientists around the world, says that more than 30,000 species are endangered, most of them as a result of human activities. "Biodiversity represents the very foundation of human existence," says a summary of the report, released Tuesday at an international conference in Jakarta. "Yet by our heedless actions we are eroding this biological capital at an alarming rate." TIME's Andrea Dorfman points out that the study is a result of the Convention on Biological Diversity, the pact signed by 160 countries at the U.N. Conference on Environment and Development in Rio de Janeiro in 1992. "This new report represents an unprecedented number of scientists," says Dorfman, "The problem with biodiversity studies in the past is that they used too small a sample to yield significant results, or studied a specific ecosystem and then make grandiose claims for the data. If this is as wide a sample as claimed, it could be very important."