Stocks of the iconic cod have collapsed. So has the lobster fishery south of Cape Cod. Maple trees are producing less sugar, wetlands such as the Great Marsh are eroding, and invasive species are on the march.
Now, a landmark United Nations report has found that the loss of plant and animal species around the world will increase drastically in the coming years, at a rate unprecedented in human history.
As many as a million animal and plant species are now threatened with extinction, many within decades, according to the report, which was produced by hundreds of scientists around the world.
That could have a grave impact on food supplies, medicines, air quality, and much more, according to the report from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services.
“It’s like we’re unraveling our life-support system,” said Stephen Polasky, professor of ecology and economics at the University of Minnesota St. Paul, one of the report’s authors. “These declines in nature will have a serious impact on our well-being, and particularly on our children and their children’s well-being.”
The report found that the average abundance of native plants and animals in the world’s major land habitats, such as the rain forests in South America and the savannas in Africa, has plummeted by at least 20 percent over the past century.
It also projects that more than 40 percent of all amphibian species, more than a third of all marine mammals, and one-third of reef-forming corals are now at risk of extinction. About 10 percent of insects appear to be threatened.
In all, the report has identified 680 vertebrates that have gone extinct since the 16th century, and more than 9 percent of domesticated breeds of mammals used for agriculture. Another 1,000 breeds are threatened.
“The overwhelming evidence . . . presents an ominous picture,” said Robert Watson, the chairman of the UN group. “We are eroding the very foundations of our economies, livelihoods, food security, health, and quality of life worldwide.”
The reasons for the losses include development, hunting, agriculture, fishing, and now, increasingly, climate change, which is likely to accelerate the loss of species in the coming years. Climate change has shifted migration patterns of many species and led to mismatches in the availability of their food supply.
Since 1980, greenhouse gas emissions have doubled, raising average global temperatures by at least 0.7 degrees Celsius, the report notes.
That warming is expected to intensify. Without any serious efforts to reduce emissions, temperatures could warm by a catastrophic 4 degrees Celsius by the end of the century.
“This report is a wake-up call to take stronger action now to protect diverse species,” said Ken Kimmell, president of the Union of Concerned Scientists, a Cambridge advocacy group that represents thousands of scientists around the country.
In New England, climate change, the march of development, and other human activity are already having a significant impact.
Maple trees are growing more slowly because of a less consistent snowpack. Rising seas erode marshes, imperiling vital ecosystems. And a range of invasive species, from hemlock woolly adelgid to Asian longhorned beetles, have proliferated and killed thousands of trees.
In New England, Kimmell and others noted, more and more land is being developed, reducing the space for natural habitats.
Although New England’s forests made a comeback over the past century, after Colonial settlers cleared most of them for agriculture, in recent decades they have been in retreat. The advance of suburban sprawl and other development now consumes about 65 acres a day of woodlands from Connecticut to Maine, according to a 2017 report by researchers at Harvard Forest, a research institute of the university in Petersham.
That report also noted how the region’s pace of land conservation has also slowed markedly, from an average of 333,000 acres per year in the early 2000s to about 50,000 acres per year since 2010.
Massachusetts, for example, has been losing about 7,000 acres of forestland a year to development, and land conservation rates are falling, the Harvard report found.
Richard Primack, a Boston University biology professor who studies the effects of climate change on plants and animals, said the losses of biodiversity are evident throughout New England. For example, more than half of the migratory bird species at a banding station in Plymouth have been found to be in decline, while more than half of wildflower species in Concord have decreased or gone extinct in the area, he said.
“Species such as elms, chestnuts, and hemlocks are being eliminated from our forests by exotic diseases and insects,” Primack said.
Scott Jackson, an associate professor of environmental conservation at the University of Massachusetts Amherst, worries about the unexpected consequences of biodiversity loss.
For example, as woolly adelgid kills more hemlock trees, there’s a threat to brook trout, he said. Hemlocks often provide shade and keep streams cool enough for the trout. Without them, he said, the trout might not survive.
“Human beings are completely dependent on other biological organisms for our survival — for food, medicine, shelter, and many other things,” he said. “Without them, we might not be able to prevent a famine or create a wonder drug that could save thousands of lives.”
Other notable findings of the report include:
■ Urban areas have more than doubled since 1992, while nearly 75 percent of the world’s fresh water is used to grow crops and cultivate livestock.
■ As many as 300 million people are at increased risk of floods and hurricanes because of a loss of coastal habitats and protection.
■ Plastic pollution has increased tenfold since 1980, with about 350 million tons of heavy metals, toxic sludge, and other waste dumped annually into the world’s waters.
Although the loss of biodiversity may seem a distant threat to many in New England, such a conclusion would be deceptive, said Christopher Neill, a senior scientist at the Woods Hole Research Center.
“When we look out the window at the forest that’s regrown in Massachusetts since 1860, things don’t look as bad as they are portrayed in this report,” he said. “We are a relatively urban, affluent state. Our consumption of food, timber, paper, energy, all push our impacts on habitat to other places.”
But Bradley Campbell, president of the Boston-based Conservation Law Foundation, said there should be no doubt about the threats posed to New England by the global loss of biodiversity.
This past weekend, for example, he attended an event to promote the protection of North Atlantic right whales. There are little more than 400 of them left.
“From agriculture and fisheries to recreation and tourism, our regional economy, culture, and way of life are on a knife’s edge,” he said. “Our ability to stem the loss of other species will tell us whether we have the capacity to save our own.”