The St. Croix National Scenic Riverway was highlighted in the Washington Post last week as an example of protected public land with challenging ecological value because of its long, skinny shape. Columnist Harry Stevens wrote about recent research related to the global goal of protecting 30 percent of the Earth for biodiversity. In a paper published last fall in the journal Nature Sustainability, a team based in Argentina found that many protected areas share a similar challenge: they’re not round enough.

The PhD student who led the study, Santiago Schauman, used the same global database of protected land that the United Nations depends on for tracking conservation. He and his colleagues analyzed 200,000 shapes, determining how much protected land is a certain distance from the border. It’s a lot.

“Ecologists are wary of oddly shaped protected areas because they have more edges where nature and humans collide,” Stevens wrote. “Schauman and his colleagues found that one-third of all the world’s protected land is within two kilometers of its borders, exposing wildlife to mining, logging, farming, ranching and other things humans do to mess with nature.”

Schuman and Stevens then looked at maps of several example protected areas, including the St. Croix and Namekagon Rivers. While the National Scenic Riverway protects 255 miles of river, the farthest any point is from the edge is a third of a mile.

“The riverway is, as superintendent Craig Hansen described it to me, ‘a thin, narrow ribbon of protection.’ Inside, the water is clean and filled with fish, and wetlands and bottomland forests along the river provide habitat for native species and rare birds like the golden-winged warbler.

“But the thin boundaries can make protection challenging. Nearby towns and farms can send polluted storm runoff into the water. Noise from roads and bridges can startle wildlife. Birds can collide with power lines and cell towers.”

– Can we save nature with crazy shapes? – Washington Post

The shape of protected areas and the “depth” of their protection is one important factor in providing habitat for imperiled species, and other ecological benefits. But there is another angle that Schauman’s study and Stevens’ article did not consider: the proximity to other protected areas.

The map below shows three types of public land: the long and skinny St. Croix National Scenic Riverway, the heavily protected areas included in the U.N.’s Database of Protected Areas, like state parks and wildlife areas, and the other types of public land included in the U.S.’s Protected Areas Database. Most of the latter category is county forest land — largely open to the public and undeveloped, but often managed intensively for timber.

Comparing the “narrow ribbon of protection” along the river to other nearby protected land shows how the ecosystem and nature preserves fit together among humanity’s more intense impacts. In many places, other public lands directly adjoin the National Scenic Riverway, effectively expanding its borders.

The idea to protect 30 percent of nature by the year 2030 was first suggested by ecologists in 2019. It has since been adopted as a goal by the United States and most other nations at a 2022 conference in Montreal, Canada. The idea has connections to the “Half-Earth Project” launched by the ecologist E.O. Wilson in 2015. Both initiatives seek to prevent species extinction and the loss of healthy ecosystems that help support human life.

“The only way to save upward of 90 percent of the rest of life is to vastly increase the area of refuges, from their current 15 percent of the land and 3 percent of the sea to half of the land and half of the sea,” Wilson wrote in a 2016 op-ed in the New York Times. “That amount, as I and others have shown, can be put together from large and small fragments around the world to remain relatively natural, without removing people living there or changing property rights. This method has been tested on a much smaller scale at the national and state park levels within the United States.”

Wilson acknowledged that protected lands can come in many shapes and sizes, but believed these preserves still played an important role in conservation. The 30 by 30 goal echoes these ideas, calling to protect “especially areas of particular importance for biodiversity and ecosystem functions and services.” It goes on to call for “ecologically representative, well-connected and equitably governed systems of protected areas and other effective area-based conservation measures,” emphasis added to indicate where the authors clearly considered how protected areas fit together in larger landscapes.

St. Croix 360 published the above map in 2022, along with an analysis of some of these issues. We found that, while a large swath of the St. Croix watershed is in some sort of public or protected ownership, only a sliver is truly managed for biodiversity and natural habitat.

“By these measures, the St. Croix River watershed is a long way from protected. All the lands in the PAD located in the basin add up to about 24 percent of the watershed. But, that includes county forests managed for logging, and even golf courses. The lands in the watershed with some known biodiversity mandate add up to 416 square miles, five percent of the watershed. Land managed for logging and other extractive purposes equals 15 percent.”

The St. Croix is truly a narrow ribbon of protection, but the river and its tributaries sew together a larger patchwork quilt of nature preserves and other public lands.

More information:

• Can we save nature with crazy shapes? – Washington Post
• The geometry of global protected lands – Nature Sustainability
• 30×30 – Campaign for Nature
• Half-Earth Project – E.O. Wilson Biodiversity Foundation