A year of big numbers startled the world into talking about nature – Science News

Some bignumbers from nature made news in 2019. They were enough of a shock to getpeople talking about the dwindling diversity of plants, animals and other lifeon Earth, and what to do about it.

Some of that dramatic news came from the Amazon, wheresatellites picked up signs of a very active start to the annual fire season.The risk of a record-breaking season renewed worries about one of the richestreservoirs of biodiversity on Earth.

In August alone, satellite-based imaging instruments calledMODIS logged 11,516 detections of fire in the large, northwestern Brazilianstate of Amazonas. The number isnt individual fires, but the number of pixels,each measuring at least a square kilometer, containing fire activity, explainsLouis Giglio of the University of Maryland in College Park, a specialist indetecting fires with remote instruments. (Higher numbers reported by some newsoutlets tallied detections from an instrument with smaller pixels.)

As the fire season drew to a close in late October, Giglioworked out the big picture for the year. While fire risk in most of SouthAmerica in 2019 was very average, Amazonas was where chaos ensued, he says.The fire detections for August exceeded all MODIS records for that month, whichgo back almost two decades, Giglio says. He ranks the 2019 fire season, fromlate June through October, as the second worst for Amazon burning, after the2005 season.

The damage distresses Alexandre Aleixo of the University ofHelsinki, who lived in the Amazon forest studying its birds for 16 years. Heworries that the lure of land for farming in Brazils pro-development politicalclimate is leading to land-clearing fires that easily jump into protectedareas, threatening the biodiversity there.

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Clearing jungles for soybeans or cattle is a good example of what a 2019 United Nations report called the main threat to nature: humans taking over wilderness for their own uses. That report made news by saying that around a million or so species of plants and animals globally about 1 in 8 face accelerated extinction unless damaged habitats are restored (SN: 6/8/19, p. 5). Dead species walking is one term used in the 1,500-plus-page draft of the report, released in an early form in May by the U.N.s Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services.

The real total of Earths imperiled species is probablylarger than a million. The U.N. panel didnt assess the abundant forms offungi, which have given humans bread, wine and antibiotics, or the vastuniverse of nonfungal microbes. Even plant and animal numbers are estimates, ofcourse; humans havent come anywhere close to giving names to all of Earthscomplex life.

The number 3 billion also startled people, prompting stories of the way things used to be. Its the estimated total population drop in birds in the United States and Canada since 1970 (SN: 10/12/19 & 10/26/19, p. 7). Digging into decades of sightings of 529 species, including records from citizen scientists, researchers detected a growing bird deficit. Many rare birds known to be in peril have continued to decline, but unnervingly, even some common birds are dwindling. Pushy and adaptable starlings dropped 63 percent, for example. Today, overall, 29 percent fewer birds, the team estimates, are flying around in the United States and Canada than there were 50 years ago.

That loss is a punch in the gut, study coauthor PeterMarra of Georgetown University in Washington, D.C., told Science News whenthe research was released. It means fewer beaks to handle many ecosystem jobs,such as nabbing insects out of the air, spreading the pollen of deep-throatedflowers or giving fruit seeds an intestinal ride to new homes.

Climate change is another of the U.N. reports top five threats to biodiversity, and fighting it by planting trees to trap greenhouse gases sparked conversation this year. Ethiopias office of the prime minister tweeted that the nation planted more than 353 million tree seedlings on a Monday in July, declaring the feat a world record.

Theres room left on Earth to plant enough trees to trap an enormous amount of carbon, estimated ecologist Tom Crowther of ETH Zurich and colleagues in a high-profile and controversial paper published in the July 5 Science. It claimed that Earth has around 0.9 billion hectares suitable for planting more trees, enough in theory to capture some 205 metric gigatons of carbon (SN: 8/17/19, p. 4).

The paper brought fresh attention to the science behind the idea, says Alan Grainger, a global change geographer at the University of Leeds in England. But more than 70 scientists joined forces to call those numbers an overestimation on October 18, also in Science. The debate over how much carbon could be captured goes on (SN Online: 11/17/19). Yet Crowther argues that planting trees across just 10 percent of the area the original paper identified would be a worthy goal. Even better, his critics say, is to avoid emitting all those greenhouse gases in the first place.

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A year of big numbers startled the world into talking about nature - Science News