In honor of Earth Day on April 22, here are five ways Nat Geo explorers are protecting the planet!

Katey Walter Anthony

1) Global warming is causing permafrost in the Arctic to thaw, which releases methane into the atmosphere, which in turn contributes to global warming. Explorer Katey Walter Anthony is researching this dangerous cycle and hoping to harness methane as a renewable energy source.

Jennifer Burney

2) How to feed 9 billion people is one of the most pressing issues threatening the planet. Through solar panels and eco-friendly stoves in rural Africa, explorer Jennifer Burney is helping tackle the problem of sustainable food production.

Osvel Hinojosa Huerta

3) Though 70% of the world is covered by water, only 2.5% of it is fresh. Explorer Osvel Hinojosa Huerta is fighting to preserve the freshwater resources of Mexico’s Colorado River Delta.

Ibrahim Togola

4) About 80% of Mali’s energy supply comes from firewood and charcoal, resulting in massive deforestation. Explorer Ibrahim Togola and his organization, Mali-Folkecenter Nyetaa (MFC), are changing this reality by introducing technology to harvest renewable energy (such as solar, wind, and biofuel) throughout the country—and hopefully setting a model for the region.

Erin Pettit

5) The noisy boundary between a glacier and the ocean can provide valuable insight into sea level rise. Using underwater instruments, explorer Erin Pettit is helping inform predictions of climate change’s impact on coastlines.