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WASHINGTON (AP) — On the ground, climate change is hitting us where it counts: the stomach — not to mention the forests, plants and animals.

A new United Nations scientific report examines how global warming and land interact in a vicious cycle. Human-caused climate change is dramatically degrading the land, while the way people use the land is making global warming worse.

Thursday's science-laden report says the combination is already making food more expensive, scarcer and even less nutritious.

"The cycle is accelerating," said NASA climate scientist Cynthia Rosenzweig, a report co-author. "The threat of climate change affecting people's food on their dinner table is increasing." 

But if people change the way they eat, grow food and manage forests, it could help save the planet from a far warmer future, scientists said

If people change their diets, reducing red meat and increasing plant-based foods, such as fruits, vegetables and seeds, the world can save as much as another 15% of current emissions by mid-century. It would also make people more healthy, Rosenzweig said.

Earth's land masses, which are only 30% of the globe, are warming twice as fast as the planet as a whole. While heat-trapping gases are causing problems in the atmosphere, the land has been less talked about as part of climate change. A special report, written by more than 100 scientists and unanimously approved by diplomats from nations around the world at a meeting in Geneva, proposed possible fixes and made more dire warnings.

"The way we use land is both part of the problem and also part of the solution," said Valerie Masson-Delmotte, a French climate scientist who co-chairs one of the panel's working groups. "Sustainable land management can help secure a future that is comfortable."

"Climate change is really slamming the land," said World Resources Institute researcher Kelly Levin, who wasn't part of the study but praised it.

And the future could be worse.

"The stability of food supply is projected to decrease as the magnitude and frequency of extreme weather events that disrupt food chains increases," the report said.

In the worst case scenario, food security problems change from moderate to high risk with just a few more tenths of a degree of warming from now. They go from high to "very high" risk with just another 1.8 degrees (1 degree Celsius) of warming from now.

Scientists had long thought one of the few benefits of higher levels of carbon dioxide, the major heat-trapping gas, was that it made plants grow more and the world greener, Rosenzweig said. But numerous studies show that the high levels of carbon dioxide reduce protein and nutrients in many crops.