PARQUE PATAGONIA, Chile -- Chilean President Michelle Bachelet signed decrees Monday creating vast new national parks using lands donated by a U.S. conservation organization in what is believed to be the largest private donation of land ever from a private entity to a country.
The agreement signed by Bachelet and Tompkins Conservation CEO Kristine McDivitt Tompkins will create the new Pumalin and Patagonia national parks while expanding others to help create a "Route of Parks."
The string of 17 parks will span more than 1,500 miles (2,400 kilometers) across the South American nation, stretching from Puerto Montt to Cape Horn.
In all, the plan ultimately seeks to increase Chile's national parkland by more than 15,600 square miles (40,400 square kilometers). Bachelet said that would expand national parklands in Chile by 38.5 percent.
"This is not only an unprecedented preservation effort," Bachelet said at a ceremony surrounded by pristine lands.
"It's also an invitation to imagine other ways of rationally occupying our lands, of creating other economic activities, of using natural resources without preying on them. In other words, it's about generating sustainable development."
Tompkins Conservation said the area that will be protected is three times the size of the United States' Yosemite and Yellowstone national parks combined, or about the size of Switzerland.
"Today is a historic day for Chile and for the world. Today, Patagonia is protected with a new network of Parks," said Rodrigo Catalan, head of conservation at the World Wildlife Fund in Chile.
The lands will safeguard millenary forests, unique fauna and flora species, and one of the purest reservoirs of water in the world, he said. But they also present daunting challenges for conservation, including how they will be financed and how they will benefit local communities.
"It's a day to celebrate, but tomorrow, we have to think how we're going to make this conservation real," he said. "How are we going to manage and finance this great legacy. It's a tremendous conservation legacy that we have to take care of for the world."
Since her husband's death in a 2015 kayaking accident, McDivitt Tompkins worked to permanently protect from development the millions of acres the couple acquired over a quarter century.
Doug Tompkins, an American conservationist and co-founder of the North Face and Esprit clothing companies, used much of his fortune to buy huge tracts of land in Patagonia, a lightly populated region of untamed rivers and other natural beauty straddling southern Chile and Argentina.
At first, his purchases of land to preserve swaths of wilderness caused suspicion and strong opposition by local politicians, loggers, power companies and nationalists who stirred rumors that he was trying to steal water and other resources. But he promised he would eventually return the land to both governments to be preserved as nature reserves or parks.
"This is a reflection of the power of dreams and ideas, built path by path," said McDivitt Tompkins.
"We're proof that nothing is impossible. No dream should go unfulfilled."
Associated Press video journalist Mauricio Cuevas reported this story in Parque Patagonia and AP writer Patricia Luna reported from Santiago. AP photographer Esteban Felix contributed to this report.