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Scientists Use Google Earth and Crowdsourcing to Map Uncharted Forests

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Scientists Use Google Earth and Crowdsourcing to Map Uncharted Forests
Hansen/UMD/Google/USGS/NASA tree cover data displayed on Global Forest Watch. Green pixels represent tree cover with greater than 20 percent canopy density but do not count trees outside of these pixels. Note, coarse pixels as shown above may be more efficient for rapidly detecting large scales of deforestation, while individual mapping techniques as described below may be more effective for monitoring land restoration and degradation.

By Katie Fletcher, Tesfay Woldemariam and Fred Stolle

No single person could ever hope to count the world's trees. But a crowd of them just counted the world's drylands forests—and, in the process, charted forests never before mapped, cumulatively adding up to an area equivalent in size to the Amazon rainforest.

Current technology enables computers to automatically detect forest area through satellite data in order to adequately map most of the world's forests. But drylands, where trees are fewer and farther apart, stymied these modern methods. To measure the extent of forests in drylands, which make up more than 40 percent of land surface on Earth, researchers from UN Food and Agriculture Organization, World Resources Institute and several universities and organizations had to come up with unconventional techniques. Foremost among these was turning to residents, who contributed their expertise through local map-a-thons.


Technical Challenges, Human Solutions

Traditional remote sensing algorithms detect tree cover in a pixel rather than capturing individual trees in a landscape. That means the method can miss trees in less-dense forests or individual trees in farm fields or grasslands, which is most often the nature of dryland areas.

Google Earth collects satellite data from several satellites with a variety of resolutions and technical capacities. The dryland satellite imagery collection compiled by Google from various providers, including Digital Globe, is of particularly high quality, as desert areas have little cloud cover to obstruct the views. So while difficult for algorithms to detect non-dominant land cover, the human eye has no problem distinguishing trees in the landscapes. Using this advantage, the scientists decided to visually count trees in hundreds of thousands of high-resolution images to determine overall dryland tree cover.

Local knowledge helped researchers ground-truth desert forest tracking. World Resources Institute

Local Map-a-thons Using Collect Earth

Armed with the quality images from Google that allowed researchers to see objects as small as half a meter (about 20 inches) across, the team divided the global dryland images into 12 regions, each with a regional partner to lead the counting assessment. The regional partners in turn recruited local residents with practical knowledge of the landscape to identify content in the sample imagery. These volunteers would come together in participatory mapping workshops, known colloquially as "map-a-thons."

To lay the groundwork for the local map-a-thon events the team identified both an entry point, usually a university, that could help recruit participants, as well as a facility with the capacity and internet to host the map-a-thon. Once trained, any given analyst could identify 80 to 100 plots per day.

Example of Collect Earth grid set for data collection.

Quality control was carried out afterwards by comparing the identified land cover with the number of trees counted. For example, if a local participant identified an image as having just three trees but later identified the same image as forest, the researchers knew there was human error and further review was required.

The Collect Earth tool allows users to navigate between multiple windows and select the best imagery for each particular data point.

These map-a-thons were designed so that people with first-hand knowledge of local landscapes could participate. No knowledge of remote sensing or any technology beyond internet literacy was required. The expertise needed was the understanding of regional landscape and land use. This practical knowledge of the region was critical as the participants were not only able to count individual trees but also identify the type of land use and trees they saw on the Google Earth images.

This research only "discovered" new forest in the sense that Columbus "discovered" the New World. The drylands forest was always there, and the people who live in the area always knew it was there. In fact, they were the only ones who had the background knowledge to identify subtleties like whether an image of a plant in their region was a shrub or actually a young tree, or if what appeared to be a tree was just a perennial plant. A few common perennial crops, including coffee and banana, looked like shrubs in the satellite images, but local participants had no problem identifying them correctly as perennial crops instead of shrubs, a distinction that would have been impossible with satellite imagery analysis alone.

Collect Earth Map-a-thon Event in Gatsibo, Rwanda.

This human identification component, along with the ability to zoom into sub-meter resolution with cheap and available technology, has helped achieve the breakthrough result of forest cover identification 9 percent higher than previously reported.

Local Ownership of the Map and the Land

Utilizing local landscape knowledge not only improved the map quality but also created a sense of ownership within each region. The map-a-thon participants have access to the open source tools and can now use these data and results to better engage around land use changes in their communities. Local experts, including forestry offices, can also use this easily accessible application to continue monitoring in the future.

Global Forest Watch uses medium resolution satellites (30 meters or about 89 feet) and sophisticated algorithms to detect near-real time deforestation in densely forested area. The dryland tree cover maps complement Global Forest Watch by providing the capability to monitor non-dominant tree cover and small-scale, slower-moving events like degradation and restoration. Mapping forest change at this level of detail is critical both for guiding land decisions and enabling government and business actors to demonstrate their pledges are being fulfilled, even over short periods of time.

The data documented by local participants will enable scientists to do many more analyses on both natural and man-made land changes including settlements, erosion features and roads. Mapping the tree cover in drylands is just the beginning.

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By Elliot Douglas

In early October, Britain's Prince William teamed up with conservationist David Attenborough to launch the Earthshot Prize, a new award for environmentalist innovation. The Earthshot brands itself the "most prestigious global environment prize in history."

The world-famous wildlife broadcaster and his royal sidekick appear to have played an active role in the prize's inception, and media coverage has focused largely on them as the faces of the campaign.

But the pair are only the frontmen of a much larger movement which has been in development for several years. In addition to a panel of experts who will decide on the winners, the prize's formation took advice from the World Wildlife Fund, Greenpeace and the Jack Ma Foundation.

With more and more global attention on the climate crisis, celebrity endorsement of environmental causes has become more common. But why do environmental causes recruit famous faces for their campaigns? And what difference can it make?

'Count Me In'

"We need celebrities to reach those people who we cannot reach ourselves," says Sarah Marchildon from the United Nations Climate Change secretariat (UNFCCC) in Bonn, Germany.

Marchildon is a proponent of the use of celebrities to raise awareness of environmental causes. In addition to promoting a selection of climate ambassadors who represent the UN on sustainability issues, Marchildon's team has produced videos with well-known narrators from the entertainment world: among them, Morgan Freeman and Mark Ruffalo.

"We choose celebrities who have a lifestyle where they are already talking about these issues," Marchildon explains.

"Sometimes they reach out to us themselves, as David Attenborough did recently. And then they can promote the videos on their own social channels which reach more people than we do — for example, if they have 20 million followers and we have 750,000."

Environmental groups focused on their own domestic markets are also taking this approach. One Germany-based organization that uses celebrities in campaigns is the German Zero NGO. Set up in 2019, it advocates for a climate-neutral Germany by 2035.

German Zero produced a video in March 2020 introducing the campaign with "66 celebrities" that supported the campaign, among them Deutschland 83 actor Jonas Nay and former professional footballer Andre Schürrle. They solicit support as well as financial contributions from viewers.

"Count me in," they say, pointing toward the camera. "You too?"

"We are incredibly grateful for the VIPs in our videos," says German Zero spokeswoman Eva-Maria McCormack.

Assessing Success Is Complex

But quantifying the effectiveness of celebrity endorsement of campaigns is not a straightforward process.

"In order to measure effectiveness, first of all you need to define what is meant by success," says Alegria Olmedo, a researcher at the Zoology Department at the University of Oxford.

Olmedo is the author of a study looking at a range of campaigns concerning pangolin consumption, fronted by local and Western celebrities, in Vietnam and China. But she says her biggest stumbling block was knowing how to measure a campaign's success.

"You need a clear theory of change," explains Olmedo. "Have the celebrities actually helped in achieving the campaign's goals? And how do you quantify these goals? Maybe it is increased donations or higher engagement with a cause."

A popular campaign in China in recent years saw famous chefs Zhao Danian and Shu Yi pledge to abstain from cooking endangered wildlife. While the pledge achieved widespread recognition, both Olmedo and Marchildon say it's difficult to know whether it made any difference to people's actions.

"In life we see a thousand messages every day, and it is very hard to pinpoint whether one campaign has actually made a difference in people's behavior," she explains.

Awareness Is Not Enough

Many campaigns that feature celebrities focus on raising awareness rather than on concrete action — which, for researcher Olmedo, raises a further problem in identifying effectiveness.

"Reach should never be a success outcome," she says. "Many campaigns say they reached a certain number of people on social media. But there has been a lot of research that shows that simply giving people information does not mean they are actually going to remember it or act upon it."

But anecdotal evidence from campaigns may suggest reach can make an active difference.

"Our VIP video is by far the most watched on our social media channels," McCormack from German Zero says. "People respond to it very directly. A lot of volunteers of all ages heard about us through that video."

However, some marketing studies have shown that celebrity endorsement of a cause or product can distract from the issue itself, as people only remember the person, not the content of what they were saying.

Choosing the Right Celebrity

Celebrity choice is also very important. Campaigns that use famous faces are often aiming to appeal to members of the public who do not necessarily follow green issues.

For certain campaigns with clear target audiences, choosing a climate scientist or well-known environmentalist rather than a celebrity could be more appealing — Attenborough is a classic example. For others, images and videos involving cute animals may be more likely to get a message heard than attaching a famous face.

"We choose celebrities who have a lifestyle where they are already talking about these issues," says Marchildon from the UN. "You need figures with credibility."

McCormack cites the example of Katharine Hayhoe, an environmental scientist who is also an evangelical Christian. In the southern United States, Hayhoe has become a celebrity in her own right, appealing to an audience that might not normally be interested in the messages of climate scientists.

But as soon as you get a celebrity involved, campaigns also put themselves at risk of the whims of that celebrity. Prince William and younger members of the royal family have come under fire in recent years for alleged hypocrisy for their backing of environmental campaigns while simultaneously using private jets to fly around the world.

But Does It Really Work?

While environmental campaigns hope that endorsement from well-known figures can boost a campaign, there is little research to back this up.

"The biggest finding [from my study] was that we were unable to produce any evidence that shows that celebrity endorsement of environmental causes makes any difference," says Olmedo.

This will come as a blow to many campaigns that have invested time and effort into relationships with celebrity ambassadors. But for many, the personal message that many celebrities offer in videos like that produced by German Zero and campaigns like the Earthshot Prize are what counts.

The research may not prove this conclusively — but if the public believes a person they respect deeply personally cares about an important issue, they are perhaps more likely to care too.

"I personally believe in the power this can have," says Marchildon. "And if having a celebrity involved can get a single 16-year-old future leader thinking about environmentalist issues — that is enough."

Reposted with permission from DW.

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