Why protecting mangroves is key to mitigating climate change

When Angelo Bernardino’s family had Sunday lunches at a favorite restaurant in Vitória, his hometown on Brazil’s Atlantic coast, “right next to us were mangroves,” the National Geographic Explorer and marine ecologist recalls. The trees teemed with mosquitoes but were “beautiful and pristine.” He was captivated.

After decades studying ocean ecosystems, Bernardino now places special emphasis on mangroves. He’s part of the National Geographic and Rolex Perpetual Planet Amazon Expedition, a series of scientific research projects spanning the Amazon River Basin.

Coastal trees and shrubs characterized by their gnarled, exposed roots, mangroves thrive in places other plants don’t: where rivers meet oceans in tropical and subtropical regions, typically in brackish, but sometimes in fresh, water. 

Examining mangroves means racing against time, as their roots are accessible only when the tide is out. Bernardino and colleagues wait in their boat for low tide, then wade into the tangle of roots and take soil samples, measurements, and photos. After about four hours, they scramble to leave before a 12-foot-tall wave, the pororoca, rushes in and floods their workspace.

Mangroves are vital to the region’s climate change mitigation efforts, Bernardino says, as they absorb salt and carbon and need little oxygen. The Brazilian government’s current emissions reduction goals don’t stress mangrove protection; Bernardino hopes the data he gathers will influence that policy.

Some 2,500 acres of Amazon mangroves fall to deforestation each year; cutting them releases up to four times as much carbon as cutting the same amount of upland trees, Bernardino’s team recently found. “Now we know,” he says, “what happens when mangroves are disturbed.”