The WWF established this decline by analyzing 10,000 populations of over 3,000 species. The data was then organized into a Living Planet Index (LPI) for all 45,000 known vertebrates. According to the LPI, the population of mammals, birds, reptiles, amphibians and fish has declined 52 percent since 1970.
The organization cites the specific causes in its Living Planet Report 2014: 37 percent of animals have been killed off due to exploitation, 31 percent through habitat alteration, 13 percent from habitat loss and 7 percent due to climate change.
“Put another way,” WWF writes, “in less than two human generations, population sizes of vertebrate species have dropped by half.”
The Guardian has organized the findings in a simple graph:
Freshwater ecosystems suffered the most, losing 75 percent of their populations since 1970.
“Rivers are the bottom of the system,” says Dave Tickner, WWF’s chief freshwater adviser. “Whatever happens on the land, it all ends up in the rivers.”
“The scale of the destruction highlighted in this report should be a wake-up call for us all,” says chief executive of WWF-UK David Nussbaum. “But 2015 – when the countries of the world are due to come together to agree on a new global climate agreement, as well as a set of sustainable development goals – presents us with a unique opportunity to reverse the trends. We all – politicians, businesses and people – have an interest, and a responsibility, to act to ensure we protect what we all value: a healthy future for both people and nature.”