Worldwide populations of mammals, birds and other vertebrates have fallen by an average of 52 percent in the past 40 years, according to the Living Planet Index report recently released by the World Wildlife Fund.

Many forms of human activity are responsible for the alarming rate of animal decline. Habitat depletion, overexploitation, pollution, invasive species and other problems all contribute to the loss. Climate change is both a cause and a result of species and habitat loss.

The World Wildlife Fund released its report just a week after the United Nations Climate Summit, a series of meetings meant to spur global action on climate change. During the summit, leaders in government, finance and business promised to improve sustainable practices and to mitigate climate change.

The United States is the second-largest overall contributor to climate change through carbon pollution. Additionally, it is the largest per-capita contributor. The country is set to fulfill some of its environmental promises, including a 17 percent reduction in carbon emissions by 2020.

The Living Planet Index’s eye-opening report — half the planet’s vertebrates gone in four decades and little likelihood of improvement without concrete action — is a reminder of the need for improved environmental policies. We urge leaders in both politics and business in the U.S. to consider these numbers and to follow through on their commitments. We must protect the environment and help stem accelerated global climate change if business is to continue as normal.