Africa Shows the Power of Growing Trees from Seed
Storms, disease and the rigors of urban life have caused high mortality rates among trees in the United States. African countries found trees that sprout naturally are more resilient.
The West African country of Niger is hot. And it’s getting hotter. High temperatures in the landlocked country, which is nearly twice the size of Texas, average around 105 degrees Fahrenheit during the warm season. Climate change is expected to hit Niger and its African neighbors worse than any other nation or continent, according to the United Nations. Droughts in the Sahel -- a strip of grassland that stretches like a belt across the width of Africa, just south of the Sahara Desert -- have become more regular since the 1960s. And a 2009 study from Stanford University’s Program on Food Security and the Environment predicted that six countries in the Sahel -- Mali, Burkina Faso, Niger, Sierra Leone, Senegal and Chad -- will face temperatures by 2050 that are “hotter than any year in historical experience.”
Yet the Sahel is greener today than it has been in 40-plus years, in part because the region embraced a simple weapon against climate change: trees. Not planting trees, as Mark Hertsgaard wrote in his 2011 book, “Hot: Living Through the Next 50 Years on Earth,” but growing them.
For generations, farmers throughout the Sahel had cleared tree saplings as they sprouted in their fields. The trees were a problem because they competed with crops. But as crop yields began to plummet in the 1970s and ’80s, more farmers opted to let the trees grow. At the same time, they also implemented smarter farming methods: fortifying soil with manure, growing different crops on the same piece of land and relying on natural predators instead of pesticides to combat pests.
Ultimately, mixing trees and crops -- a practice called “farmer-managed natural regeneration” -- worked. As the trees grew, crop yields increased and the Sahel went from brown to green. Comparing satellite images from the 1970s to today shows just how successful the practice has been: Hertsgaard found that farmers in Niger have grown more than 200 million trees and rehabilitated 12.5 million acres of land.
The key here is that farmers didn’t plant partially grown saplings; they grew the trees from seed. Planting trees, in general, is less successful (in the Sahel, studies found that 80 percent of planted trees died within the first two years). Trees that sprout naturally tend to be native species, and therefore, are more resilient. In the U.S., urban tree planting campaigns like MillionTreesNYC and Million Trees LA have struggled with high mortality rates due to heavy storms, disease and the rigors of urban life -- pollution, rock salt, acidic soil and other assaults.
Should cities like New York and Los Angeles scrap their tree-planting programs? No. With some 4 million trees disappearing every year from American urban areas, according to the U.S. Forest Service, a commitment to planting new trees is essential for environmental health. But the experience in the Sahel region might be cause for urban arborists in the U.S. to think about growing more trees from seed.
Meanwhile, there’s the question of preservation. Maintaining the health of mature trees can be as important as growing new ones. In the Sahel, that became a question of stewardship: Historically, trees were often considered property of the state, and individual farmers had little incentive to grow or protect them. When food production suffered, however, governments along the Sahel began changing their laws to recognize property rights. When farmers owned their trees, they began to see the benefits of growing and preserving them.
In the U.S., the opposite tack may be effective. Some cities, including San Francisco, treat mature trees like historic buildings. Removing or altering one -- even on private land -- is heavily regulated.
Trees are essential in the fight to mitigate climate change. They suck up harmful carbon dioxide. That’s as important in San Francisco and New York as it is in Niger. And that may be good reason to start thinking about seeds.
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