Poachers have killed more than 90 percent of Zambia's elephants since the 1950s. In response, villagers banded together to protect those in North Luangwa National Park last year.
Warren's plan includes ending fossil fuel drilling on public lands, eliminating entrance fees for national parks, and mandating spending for the Land and Water Conservation Fund.
New research shows that culling invasive, non-native animals on just 169 islands around the world over roughly the next decade could help save almost 10 percent of island-dwelling animals at risk of extinction.