tree cover

California Trees Are Dying | Earth Wise

August 19, 2022 By EarthWise Leave a Comment

California relies on extensive forests to help reduce the amount of carbon dioxide entering the atmosphere. But extensive drought and increasingly frequent wildfires have been reducing the state’s tree population for the past three decades.

A comprehensive study by a team of scientists from the University of California Irvine used satellite data to study vegetation changes between 1985 and 2021. Across the entire state, tree cover area has declined 6.7% over that time period. The results varied from region to region across the state.

Southern California exhibited the sharpest decline, where 14% of the tree population in local mountain ranges vanished, potentially permanently. In the Sierra Nevada mountains, tree populations were relatively stable until about 2010. After that, a severe drought followed by historically large wildfires resulted in a 8.8% die-off of trees. The northern parts of the state, with higher rainfall and cooler temperatures, fared better, being able to more easily recover from wildfires.

The study goes beyond measuring the tree population of the state and its effects on carbon storage. The data is also important for understanding how changes in forest cover affects water resources and fire behavior in the state.

The decline of trees in California is affecting the carbon storage abilities of the state. The satellite survey showed that as the tree populations have dropped, the state’s coverage of shrubs and grasses has risen, possibly indicating that permanent ecosystem shifts are occurring. The forces contributing to the decline of trees in California are not going away any time soon. As a result, the threat to California’s ability to mitigate the effects of climate change continues to grow.

**********

Web Links

UCI study: California’s trees are dying, and might not be coming back

Photo, posted March 24, 2016, courtesy of David Fulmer via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Tracking Endangered Species From Space | Earth Wise

March 4, 2021 By EarthWise Leave a Comment

Scientists at the University of Bath and the University of Oxford in the UK have developed a technique for remotely surveying elephants and other wildlife using satellite images and deep learning. The technique has the same accuracy as human counts done on the ground or from low-flying airplanes.

The new computer algorithm can analyze high-resolution satellite images and detect African elephants in both grasslands and forests. Previous techniques for monitoring wildlife from space were limited to homogenous habitats, such as the case of tracking whales in the open ocean.

On-the-ground or airplane surveys to monitor animal numbers are expensive and time-consuming. Satellites can collect nearly 2,000 square miles of imagery in a few minutes thereby eliminating the risk of double counting and reducing a process that previously took weeks to just a few days. The use of satellites also eliminates the logistical problems of monitoring species populations that cross international borders.

Accurate monitoring is important for efforts to save endangered species. There are only 40,000 – 50,000 African elephants left in the wild. It is essential to know where the animals are and how many there are in various locations. The new method is able to count elephants in mixed ecosystems, such as savannah and forests, where tree cover would previously have made satellite tracking difficult.

With satellite imagery resolution increasing every few years, it should be possible to see ever-smaller things in greater detail. The new algorithm works well for elephants; it may eventually become practical to track animals as small as an albatross from space.

**********

Web Links

A New Way to Track Endangered Wildlife Populations from Space

Photo, posted March 15, 2008, courtesy of Michelle Gadd/USFWS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Trees And The Future Of Cities

April 16, 2019 By EarthWise Leave a Comment

The shade of a single tree is a welcome source of relief on a hot summer day. But even a relatively small patch of woods can have a profound cooling effect. A new study at the University of Wisconsin-Madison looks at the role trees play in keeping towns and cities cool.

According to the study, the right amount of tree cover can lower daytime temperatures in the summer by as much as 10 degrees. The effects are noticeable from neighborhood to neighborhood and even on a block-by-block basis.

Cities are well-known to be hot spots due to the urban heat islanding effect. Using trees to keep temperatures more comfortable in cities can make a big difference for the people who live and work there.

The man-made structures of cities – roads, sidewalks, and buildings – absorb heat from the sun during the day and slowly release it at night. Trees, on the other hand, not only shade those structures from the sun, but they also transpire -or release water in the air through their leaves – which helps to cool things down.

According to the study, to get maximum cooling benefits, tree canopies must exceed forty percent, meaning that city blocks need to be nearly halfway covered by tree branches and leaves. To get the biggest bang for the buck, cities should start planting more trees in areas that are already near the forty percent threshold. But

trees can’t just be in parks. They need to be in places where people are active.

If we want the places where we live to be more comfortable and resilient in a warming world, we need to plant more trees.

**********

Web Links

Study suggests trees are crucial to the future of our cities

Photo, posted May 26, 2012, courtesy of Mislav Marohnic via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.