treesource

Forest Journalism for a Sustainable Future

Not so long ago, American cities were starved for trees

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In 1919, 1,376 new Norway maples were planted along streets in Brooklyn. Photo: Department of Parks of the Borough of Brooklyn, City of New York

Many cities, in recent years, have initiated tree planting campaigns to offset carbon dioxide emissions and improve urban microclimates.

In 2007, New York City launched MillionTrees NYC, a program designed to plant 1 million new trees along streets, in parks and on private and public properties by 2017. They hit their goal two years ahead of time.

These programs are popular for a reason: Not only do trees improve the city’s appearance, but they also mitigate the urban heat island effect – the tendency for dense cities to be hotter than surrounding areas. Studies have shown that trees reduce pollutants in the air, and even the mere sight of trees and the availability of green spaces in cities can decrease stress.

But as I show in my new book, “Seeing Trees: A History of Street Trees in New York City and Berlin,” trees weren’t always a part of the urban landscape. It took a systematic, coordinated effort to get the first ones planted.

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Climate change: Yellowstone’s forests could be replaced by grasslands by mid-century

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For a study looking at the ability of trees in Yellowstone National Park to recover from fire under climate conditions that are warmer and drier than they have been historically, researcher Winslow Hansen planted tree seeds in soils from areas of the park like this one, which recently burned. Photo: Ann K. Olsson

The fires in Yellowstone National Park began to burn in June 1988. A natural feature of the landscape, park managers expected the flames to fizzle by July, when rains historically drenched the forests and valleys of the world’s first national park.

But the rains never came. In unusually hot, dry and windy conditions, more fires erupted, spreading in and around the park until September. By then, 36 percent of Yellowstone was affected. Firefighting efforts topped $120 million.

Yellowstone experiences large fires every 100 to 300 years, and its flora and fauna are adapted to that schedule. Lodgepole pines like those at higher elevations in the park have pine cones that open in fire, releasing seeds to replenish a post-burn forest. But it takes time for trees to mature and the forests to recover — time that a changing climate has been depriving the forest of over the last three decades.

A new study published Jan. 17, 2019 in Ecological Monographs, led by Winslow Hansen and his former graduate adviser, University of Wisconsin–Madison Professor of Integrative Biology Monica Turner, shows that some of Yellowstone’s forests may now be at a tipping point. They could be replaced by grassland by the middle of this century.

“It’s terrifying in some ways,” Turner says. “We are not talking many years away. Today’s college students will be mid-career. It feels like the future is coming at us fast.”

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Climate change and wildfires: How do we know there’s a link?

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Flames from the Camp Fire burn near a home atop a ridge near Big Bend, California, on November 10, 2018. Photo: JOSH EDELSON/AFP/Getty Images

Once again, the summer and fall of 2018 in the Northern Hemisphere has brought us an epidemic of major wildfires.

These burn forests, houses and other structures, displace thousands of people and animals, and cause major disruptions in people’s lives. The huge burden of simply firefighting has become a year-round task costing billions of dollars, let alone the cost of the destruction. The smoke veil can extend hundreds or even thousands of miles, affecting air quality and visibility. To many people, it has become very clear that human-induced climate change plays a major role by greatly increasing the risk of wildfire.

Yet it seems the role of climate change is seldom mentioned in many or even most news stories about the multitude of fires and heat waves. In part this is because the issue of attribution is not usually clear. The argument is that there have always been wildfires, and how can we attribute any particular wildfire to climate change?

As a climate scientist, I can say this is the wrong framing of the problem. Global warming does not cause wildfires. The proximate cause is often human carelessness (cigarette butts, camp fires not extinguished properly, etc.), or natural, from “dry lightning” whereby a thunderstorm produces lightning but little rain. Rather, global warming exacerbates the conditions and raises the risk of wildfire.

Even so, there is huge complexity and variability from one fire to the next, and hence the attribution can become complex. Instead, the way to think about this is from the standpoint of basic science – in this case, physics. [Read more…]

In a warming world, risk of ‘cascading’ natural disasters on the rise

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Thomas Fire, Ventura, CA, Los Padres NF, 2017
Firefighters watch the approach of last fall’s Thomas Fire in Ventura, California, Los Padres National Forest. Photo: U.S. Forest Service

In a warming world, the dangers from natural disasters are changing. In a recent commentary, we identified a number of costly and deadly catastrophes that point to an increase in the risk of “cascading” events – ones that intensify the impacts of natural hazards and turn them into disasters.

Multiple hazardous events are considered cascading when they act as a series of toppling dominoes, such as flooding and landslides that occur after rain over wildfires. Cascading events may begin in small areas but can intensify and spread to influence larger areas.

This rising risk means decision-makers, urban planners and risk analysts, civil engineers like us and other stakeholders need to invest more time and effort in tracking connections between natural hazards, including hurricanes, wildfires, extreme rainfall, snowmelt, debris flow, and drought, under a changing climate. [Read more…]

Study: Climate change impacts are most severe in U.S. national parks

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Signs of climate change and its impact on natural ecosystems are abundant in America’s national parks, including Yosemite, where wildfires have shrouded the iconic landscape in smoke for several summers running. (Photo: Sherry Devlin)

Human-caused climate change is disrupting ecosystems and people’s lives around the world. It is melting glaciers, increasing wildfires, and shifting vegetation across vast landscapes. These impacts have reached national parks around the world and in the United States. Until now, however, no analysis had examined climate change trends across all 417 U.S. national parks.

The United States established the first national park in the world, Yellowstone National Park, in 1872. U.S. national parks today protect some of the most irreplaceable natural areas and cultural sites in the world. Colleagues and I aimed to uncover the magnitude of human-caused climate change on these special places. We conducted the first spatial analysis of historical and projected temperature and precipitation trends across all U.S. national parks and compared them with national trends.

Our newly published results reveal that climate change has exposed the national parks to conditions hotter and drier than the country as a whole. This occurs because extensive parts of the parks are in extreme environments – the Arctic, high mountains, and the arid southwestern United States. [Read more…]