A significant decline in biodiversity is hitting low-income countries least able to afford it, the World Wildlife Fund reported in Switzerland.

"Overall, biodiversity has declined by 28 percent around the world since 1970. But in low-income countries the loss is particularly important -- it reaches 60 percent. The depletion of the natural systems is hitting hardest in countries that can least afford it," said Jim Leape, director general of WWF International, introducing the organization's 2012 Living Planet Report Monday in Geneva.

The environmental organization's report, released every two years, looks at biodiversity around the world and at humanity's ecological footprint, the pressure put on land and water.

That footprint has increased significantly, WWF officers said.

"We are using 50 percent more resources than the earth can support. Today we are living as if we had 1 1/2 planets," Leape said.

"If we continue like this, by 2050 we will need three planets. Our pattern of consumption is unsustainable."

On average, the WWF said, high-income countries have an ecological footprint that is five times that of low-income ones.

The report came out five weeks ahead of the United Nations Sustainable Development Conference, or Rio+20, in Rio de Janeiro.

"The challenges underlined in the Living Planet Report are clear," Leape told Inter Press Service. "Rio+20 can and must be the moment for governments to set a new course towards sustainability."