A study published in March in Tropical Conservation Science offers the latest look at the biological value of so-called secondary forests. An international team of ecologists and volunteers spent a year and a half identifying every bird, amphibian, reptile and medium-to-large mammal they could find on some 800 recovering hectares within Peru’s Manu Biosphere Reserve, a UNESCO World Heritage site. Their final count of 570 species amounted to 87 percent of those known to exist in neighboring old-growth, or primary, forests and included many imperiled creatures, such as shorteared dogs and giant armadillos. The team even found what could be new frog species.
The Manu study area represents a “best-case scenario” for secondary forest biodiversity, says Andrew Whitworth of the University of Glasgow in Scotland, who conducted the study in partnership with the Peruvian nonprofit Crees Foundation. Success is more likely at Manu because a longtime hunting and logging ban is in place, and animals can easily wander in from the extensive old-growth zones nearby.
Nevertheless, even lesser quality sites in the beginning stages of renewal provide myriad environmental benefits, including watershed preservation and wildlife corridors. Secondary-growth forests also reduce carbon dioxide pollution: in February researchers reported that regenerating tropical forests pull about 11 times more carbon from the atmosphere than old-growth swaths (which have already approached the maximum amount of carbon they can sequester).
“We’re not saying at any point that this is more important than primary forest,” Whitworth says. “But with good protection and time to regenerate, secondary forests could become very valuable again.” Robin Chazdon, an ecology professor at the University of Connecticut, and her colleagues agree, quipping in a paper that regenerating forests are “like a good Bordeaux,” in that their worth appreciates with each passing year.
“We can’t stop [at] protecting old growth,” says Chazdon, who is advising Brazil on how to revitalize its decimated Atlantic Forest. “That’s not going to be enough.”
