(CNN) Humans have damaged around a quarter of ice-free land on Earth, United Nations scientists warned in a major report Thursday, stressing that further degradation must be stopped to prevent catastrophic global warming .

The warning comes almost a year after the Intergovernmental Panel on Climate Change (IPCC) concluded in a landmark report that we only have until 2030 to drastically reduce our dependence on fossil fuels and prevent the planet from reaching the crucial threshold of 1.5 degrees Celsius above pre-industrial levels.

The second IPCC report highlights the vicious cycle of climate change and land degradation.

"We humans affect more than 70% of ice-free land, a quarter of this land is degraded. The way we produce food and what we eat contributes to the loss of natural ecosystems and declining biodiversity," said Valérie Masson-Delmotte, co-chair of the IPCC.

Deforestation and agriculture also fuel global warming, by weakening land's capacity to draw down carbon dioxide from the atmosphere and emitting vast amounts of greenhouse gases.

"When land is degraded, it reduces the soils ability to take up carbon and this exacerbates climate change. In turn, climate change exacerbates land degradation in many different ways. Today 500 million people live in areas that experience desertification," Masson-Delmotte said.

Scientists say that we must immediately change the way we manage land, produce food and eat less meat in order to halt the climate crisis.

But the report does offer hope, there are major opportunities to reverse the damage, the IPCC notes.

Planting trees on farmland , known as agroforestry, better soil management and reducing food waste are win-win solutions which can boost land productivity and reduce emissions.

Here are five key takeaways from the IPCC report:

Land the size of South America has been degraded

Human use takes up over 70% of the world's ice-free land surface, according to the IPCC report.

They degrade the planet's natural resources, with chemical fertilizers, deforestation and intensive farming. In the process, humans have damaged two billion hectares of land, the size of South America.

As a result, this land is less fertile and captures smaller quantities of carbon emissions from the atmosphere, according to Stephen Cornelius, the World Wildlife Fund's (WWF) chief advisor on climate change.

"The way we use land is driving the climate crisis," he told CNN. "Ecosystem conversion releases greenhouse gas emissions.

Land use, including agriculture and deforestation, produces almost a quarter of the world's greenhouse gas emissions.

We need to stop wasting food and eat less meat

The IPCC report stresses that food waste and meat consumption will need to be reduced if we want to slash global emissions.

Both are big contributors to global warming -- with food waste producing between 8-10% and livestock 14.5% of global emissions, according to WWF.

According to the report, 25-30% of all food produced is never eaten, while 821 million worldwide are undernourished.

If food waste was a country, it would be the third largest emitter after the US and China, according to the Waste and Resources Action Programme (WRAP), a non-profit working to reduce global waste.

"The fact that more than one billion tonnes of food never gets consumed while one in nine people go to bed hungry is a travesty," said Claire Kneller, head of food at WRAP.

If the United Nations goal of halving food waste by 2030 is to be met, countries should start measuring waste and adopt their own reduction goal, according to Kneller.

"We will not tackle the impact of climate change if we do not fix our global food system," she said.

We need to restore natural carbon sinks

Forests and wetlands are important carbon sinks, but have been greatly diminished by human activities, the IPCC warns, and their ability to capture carbon could continue to decrease depending on human actions.

Between 2007-2016, land removed 29% of total CO2 emissions from the atmosphere.

Peatlands -- a type of wetlands -- can hold carbon for centuries, but more intense droughts, floods and wildfires could trigger the release of carbon from the soil.

Sustainable soil management and agroforestry are key solutions that "deliver carbon sequestration in soil or vegetation," the report notes.

Land restoration "represents a fantastic opportunity to draw down carbon from the atmosphere," Cornelius said.

Photos: Effects of global warming around the world Melting polar ice caps – The consequences of climate change go far beyond warming temperatures, which scientists say are melting the polar ice caps and raising sea levels. Click through the gallery for a look at 10 other key effects of climate change, some of which may surprise you. Hide Caption 1 of 11 Photos: Effects of global warming around the world Drought – In the coming decades climate change will unleash megadroughts lasting 10 years or more, according to a new report by scholars at Cornell University, the University of Arizona and the U.S. Geological Survey. We're seeing hints of this already in many arid parts of the world and even in California, which has been rationing water amid record drought. In this 2012 photo, a man places his hand on parched soil in the Greater Upper Nile region of northeastern South Sudan. Hide Caption 2 of 11 Photos: Effects of global warming around the world Wildfires – There's not a direct link between climate change and wildfires, exactly. But many scientists believe the increase in wildfires in the Western United States is partly the result of tinder-dry forests parched by warming temperatures. This photo shows a wildfire as it approaches the shore of Bass Lake, California, in mid-September. Hide Caption 3 of 11 Photos: Effects of global warming around the world Coral reefs – Scientists say the oceans' temperatures have risen by more than 1 degree Fahrenheit over the last century. It doesn't sound like much, but it's been enough to affect the fragile ecosystems of coral reefs, which have been bleaching and dying off in recent decades. This photo shows dead coral off the coast of St. Martin's Island in Bangladesh. Hide Caption 4 of 11 Photos: Effects of global warming around the world Food prices – food prices. Here, in 2010, workers on combines harvest soybeans in northern Brazil. Global food experts have warned that climate change could double grain prices by 2050. A U.N. panel found in March that climate change -- mostly drought -- is already affecting the global agricultural supply and will likely drive upfood prices. Here, in 2010, workers on combines harvest soybeans in northern Brazil. Global food experts have warned that climate change could double grain prices by 2050. Hide Caption 5 of 11 Photos: Effects of global warming around the world Pollen allergies – Are you sneezing more often these days? Climate change may be to blame for that, too. Recent studies show that rising temperatures and carbon dioxide levels promote the growth of weedy plant species that produce allergenic pollen. The worst place in the United States for spring allergies in 2014, according to the Asthma and Allergy Foundation of America? Louisville, Kentucky Hide Caption 6 of 11 Photos: Effects of global warming around the world Deforestation – forests. Invasive species such as the bark beetle, which thrive in warmer temperatures, have attacked trees across the North American west, from Mexico to the Yukon. Climate change has not been kind to the world'sforests. Invasive species such as the bark beetle, which thrive in warmer temperatures, have attacked trees across the North American west, from Mexico to the Yukon. University of Colorado researchers have found that some populations of mountain pine beetles now produce two generations per year, dramatically boosting the bugs' threat to lodgepole and ponderosa pines. In this 2009 photo, dead spruces of the Yukon's Alsek River valley attest to the devastation wrought by the beetles. Hide Caption 7 of 11 Photos: Effects of global warming around the world Mountain glaciers – The snows capping majestic Mount Kilimanjaro, Africa's highest peak, once inspired Ernest Hemingway. Now they're in danger of melting away altogether. Studies suggest that if the mountain's snowcap continues to evaporate at its current rate, it could be gone in 15 years. Here, a Kilimanjaro glacier is viewed from Uhuru Peak in December 2010. Hide Caption 8 of 11 Photos: Effects of global warming around the world Endangered species – Polar bears may be the poster child for climate change's effect on animals. But scientists say climate change is wreaking havoc on many other species -- including birds and reptiles -- that are sensitive to fluctuations in temperatures. One, this golden toad of Costa Rica and other Central American countries, has already gone extinct. Hide Caption 9 of 11 Photos: Effects of global warming around the world Animal migration – It's not your imagination: Some animals -- mostly birds -- are migrating earlier and earlier every year because of warming global temperatures. Scholars from the University of East Anglia found that Icelandic black-tailed godwits have advanced their migration by two weeks over the past two decades. Researchers also have found that many species are migrating to higher elevations as temperatures climb. Hide Caption 10 of 11 Photos: Effects of global warming around the world Extreme weather – The planet could see as many as 20 more hurricanes and tropical storms each year by the end of the century because of climate change, according to a 2013 study published in the Proceedings of the National Academy of Sciences. This image shows Superstorm Sandy bearing down on the New Jersey coast in 2012. Hide Caption 11 of 11

Climate change is threatening food security

"The food system is both a leading cause and a casualty of climate change," according to Joao Campari, who leads WWF's global food practice.

Climate change increases the frequency and intensity of extreme weather events, such as droughts and floods, which destroy crops and critical farming infrastructure.

Read more: What is climate change? Your questions answered

It's not just extreme weather that is threatening farming -- climate change is also changing what types of crops can grow in certain locations by making it too hot or too dry.

Campari told CNN the food system must "urgently" be reformed to avoid catastrophic global warming.

Food production uses 34% of land worldwide and contributes up to 75% of deforestation, he said.

To stave off the worst effects of climate change, humans need to stop converting land and destroying the soil with fertilizers and by cutting down trees, said Campari, adding that we already have enough farmland to feed the global population.

Bioenergy is not the answer

In its report last year, the IPCC warned that keeping global temperatures at 1.5°C above pre-industrial levels would require removing carbon dioxide from the atmosphere, using techniques such as Bioenergy with Carbon Capture and Storage (BECCS).

But in its latest report, the IPCC said that quickly rolling out this technology on a large scale "could greatly increase demand for land conversion."

Ramping up bioenergy production through the use of fertilizers and irrigation could erode soil, increase water scarcity and threaten food security, the report notes.

Claudia Ringler, deputy director at the International Food Policy Research Institute (IFPRI), told CNN that biofuels are not a scalable solution.

The world would have to convert 7.2 million square kilometers, 45% of the Earth's cropland, into bioenergy crops to keep global temperatures at 1.5°C, according to the most energy-intensive scenario outlined in the 2018 IPCC report.

"It's not possible, not at the rate they are proposing," Ringler said, explaining that the conversion of this much land would lead to a huge spike in global food prices and drive insecurity.