How to discern a forest behind trees: creating a three-dimensional image of the world's forests

How to discern a forest behind trees: creating a three-dimensional image of the world's forests.

Seeing Forests for the Trees and the Carbon: Mapping the World's Forests in Three Dimensions

By Michael Carlowicz Design by Robert Simmon January 9, 2012

Translation Lockywolf, 2012-13



Trees cool and moisten the air around them, and also enrich it with oxygen. They reduce wind speed and shield the earth from direct sunlight. The forest is home to countless species. The forest strengthens the soil and slows the movement of groundwater. For humans, forest is a source of food, fuel, medicines and building materials.

The amount of forests determines the carbon budget of the Earth.





(Photograph © 2007: Duncan.)

Is it possible to compensate for the amount of carbon emitted by "landscaping the landscape"? Should I plant trees, or cut down cuttings? Does it matter where in the world?

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Scientists estimate that mankind each year emit about nine billion tons of carbon (mainly in the form of carbon dioxide) into the atmosphere by burning fossil fuels and due to changes in the landscape. About four billion tons remain in the atmosphere, and about two billion are dissolved in the ocean. The remaining three billions go to different ecosystems on earth, but which ones remain the question.



It is believed that most of the emitted, both due to natural processes, and due to human activity, carbon is of forest origin in the atmosphere. Forests cover about 30 percent of the Earth’s surface, they account for about 50 percent of the plants covering the Earth. Nearly 45 percent of all carbon stocks on Earth are found in forests.





(Map by Robert Simmon, based on data from the MODIS Land Cover Group, Boston University.)

Forests cover 30 percent of the Earth’s surface.



Was carbon stock in forests more or less in the past? Will it increase with time?

Science does not know how much carbon forest is able to accumulate.

She also knows that human activity has transferred a lot of carbon from long-term, sustainable forms, such as coal, fossil fuels or old forests into short-lived forms that have a direct short-term impact on the environment. For example, when we cut down forests, we remove tall, old trees that can accumulate carbon in the trunk, branches, and leaves for hundreds of years. We replace them with pastures or plowed fields, which can accumulate less carbon and for a shorter period. Urban landscapes are generally practically unable to accumulate carbon.





(Photograph © 2007 Aviruthia.)

In the eighty years since logging, this forest in British Columbia has never been able to recover to its original power.



“The world's largest carbon sink is our forests and trees,” says Steve Running, an ecologist at the University of Montana. “But he is also his greatest source. That is, one of the most important things we can do to understand the structure of the carbon budget of the Earth is to study how much carbon is in the forests. ”

The key indicator is the amount of biomass - the total mass of all organisms living in a selected area. The rule of thumb established by environmentalists states that carbon is half the dry biomass of a tree. That is, by estimating how much biomass is contained in all trees of all forests, one can estimate how much carbon is stored on land. By repeating these measurements from year to year, one can understand how carbon moves around the planet.

According to popular belief, trees are the key to solving all the problems of our carbon budget. Based on economic considerations, it can be assumed that the problem will be solved if you grow trees and plant a landscape. But will it really help? Can it just cut down less? Does it matter where it is geographically?

To answer these questions, for a start it is worth understanding how much carbon is present in the trees at the moment.

Three-dimensional image of the forest

Scientists use a variety of methods to study the forest and its biomass. Trees are studied from root to crown, expeditions were undertaken to count the number of trees, parameters of individual trees were measured, for example, the thickness of the trunks. Gradually, methods using aerial surveys have emerged. Photographic, radar and lidar studies of various types of forests were made.



With the help of satellites, regional and global measurements of the amount of "greens" on the surface of the earth were made and the volume of flora estimated. At the same time there were attempts to distinguish forests from bushes by satellite images.





Student Kelly McManus measures the circumference of a tree in a coastal forest in Virginia. Ground studies are vital to ensure the accuracy of aerial and satellite studies of the plant world .. (NASA photograph courtesy Lola Fatoyinbo.)



But in order to estimate the biomass, it is necessary to know the territory, density and, most importantly, the height of the trees. Scientists have managed to measure all of this on a small scale, but using traditional methods in global research is excessively expensive and time consuming.

“We need to see terrestrial vegetation in three dimensions,” says John Ranson, an ecologist at NASA’s Goddard Space Flight Center, a forest specialist. “By measuring the height of trees, we can then estimate the amount of biomass located above sea level and estimate the amount of carbon stored in forests. The more accurate the measurements, the more accurate our carbon estimates. ”

The first forest height map on Earth came out in 2010. It was made by Michael Lefski from the University of Colorado, combining many horizontal views of the earth's surface, made on NASA's Terra and Aqua satellites using the MODIS Radiation Spectroradiometer, with height maps from the ICESat satellite. (NASA's Ice, Cloud, and land Elevation Satellite)





The height of forests in the world varies from more than 40 meters in the Northwest United States to less than 20 meters in the sub-Arctic. On this map, the darker the green color is, the higher the forest is. [NASA Earth Observatory map, using data from Michael Lefsky, Colorado State University].



The result was a map showing that the highest forests are concentrated in the North-West of the Pacific Coast of North America and in certain regions of Southeast Asia, and that the forests of medium height cover vast territories of Canada and Eurasia. The highest species - conifers: Douglas fir, Western hemlock, mahogany, sequoia - grow more than forty meters. Taiga forests - pine, spruce and fir, usually below 20 meters. In the middle are the deciduous forests of Europe and the United States, as well as untouched tropical forests, which on average reach 25 meters.

The core of the work was the data of the Laser Altimeter (Geoscience Laser Altimeter System (GLAS)) on the ICESat satellite, which for 7 years of its work (2003-2009), measured the distance to the surface of the planet more than 250 million times by laser pulses. The total area of ​​the images was 2.4% of the Earth’s surface, or 24 percent of the forest area. Lefsky left to extrapolate the data and build a mathematical model of the forests surrounding the ICESat frames.





Michael Lefski gathered together direct observations of vegetation and accurate laser measurements ICESat (made along narrow paths (black lines on the map)) to build a map of forest heights. (NASA map by Jesse Allen and Robert Simmon.)



His map of the world was the first of its kind, Lefsky and his colleagues understood that many more incomprehensible could be explained with better tools and greater coverage. “This is only the first attempt,” Lefski said: “It certainly can still be improved.”

Mapping the tropics

Sassan Saatchi, a remote sensing specialist from NASA's Jet Propulsion Laboratory, is one of those who are working on the next attempt. He is engaged in satellites studying the forest, the trees and the carbon they contain. He specializes in dense thickets characteristic of the central zones of the Earth.





Tropical forests, such as these, in Gabon are an important carbon storage. (Photography courtesy Sassan Saatchi, NASA / JPL-Caltech.)



“I first visited the rainforest in 1994 when I was working on a project on the west coast of Brazil. Then he fascinated me with its complexity and beauty. ”Saatchi says. “I fell in love with this landscape, with the diversity of plants and animals, with the people who live there. Every time you see a rainforest, you find something new. For a person with a physical and mathematical education, this is one of the most complex and interesting systems for understanding and modeling. ”

It is argued that rainforests are the most productive on Earth, because they grow all year round. They accumulate an infinite amount of carbon in wood and roots, and so far scientists have managed to make only very rough numerical estimates.

“In the northern forests of the United States, Canada, and Europe, forest ranges typically have complex systems to calculate the distribution and structure of biomass by region and region,” says Saatchi. "In the tropics, we often have no idea how forest carbon is distributed at the local level."

It is known to scientists that due to deforestation and forest degradation, 10-20 percent of all CO2 emissions committed by mankind go into the atmosphere. CO2 has a noticeable greenhouse effect. Snapshots from satellites, shuttles, ISS for many years demonstrate smoke filled areas. Deforestation is a big business, interesting for both large producers of palm oil, soy, meat and leather, and small tropical farmers who are fighting for the right to go beyond the poverty line. Global demand for goods is growing, and this means that this process will not stop in the foreseeable future.





Wildfire is a popular means of clearing land from forests in the tropics. The cosmonaut with the ISS took this photo on August 14, 2010. It depicts a fire in Brazil .. (NASA astronaut photograph ISS024-E-11941, courtesy the NASA-JSC Earth Observations Lab.)



“In tropical forests there is a huge variety of plants, and the forests themselves vary greatly depending on the landscape and climate. They are studied very poorly. ”Saatchi notes. “I used all the measurement methods and mathematical tools I know to understand and map this whole complex system”



Saatchi worked with 14 colleagues from 10 institutes around the world (including Michael Lefski) to collect and analyze measurements of 4 space complexes - GLAS on the ICESat satellite, MODIS, QuickSCAT (satellite radar reflectometer) and Shuttle Radar Topography Mission - and 4079 ground-based measurements. His team mapped more than 3 million tree-height measurements and compared them with measurements taken from the ground. They calculated the amount of carbon stored in the trunk and in the roots, and then carried out an extrapolation to forest areas where there were fewer ground measurements, but about which some other parameters were known.

The result, published in May 2011, was a biocarbon map of two and a half billion hectares of forest in 75 countries on three continents. Although previous attempts have allowed mapping of tropical forests on a local or regional scale, the new map is “the first attempt to quantify the distribution of carbon systematically across all the tropics” (Saatchi words)





The map shows the total amount of carbon stored in the biomass of New Guinea, an island north of Australia that is heavily forested .. (NASA map by Robert Simmon, using data from Saatchi et al., 2011.)



Scientists have calculated that about 247 gigatons of carbon are stored in tropical forests, with 193 gigatons stored in trunks, branches and leaves, and 54 gigatons in roots. Forests in Central and South America contain 49 percent of this amount, East Asian - 26 percent, and African - 25 percent.





The accuracy of the results is almost as important as the results themselves. Areas of New Guinea, where carbon is measured well, are marked green on the map, bad red on the map. (NASA map by Robert Simmon, using data from Saatchi et al., 2011.)



Saatchi is most proud of the fact that his map not only assesses carbon stocks, but also makes clear the measurement accuracy. "The map shows an estimate of the amount of carbon at each point in the rainforest and our confidence in this assessment." A team of researchers has created mathematical models that demonstrate the margin of error in their carbon estimates. According to Saatchi, the error at the local and regional levels is 1 to 5 percent. “Assuming that biomass estimates made from the surface have 10 to 20 percent accuracy, the error on the global map is quite small,” says Saatchi.

Knowledge of uncertainties is very important for economists and resource specialists who are trying to assess the needs and possibilities of forests. It also helps scientists by pointing out areas that require more work.

“We are moving science, reducing the amount of inaccuracies, and the entire ground-based carbon transformation cycle is one big inaccuracy,” Saatchi remarks. “Data collection on the ground is extremely difficult, due to the lack of infrastructure and transportation in tropical regions. Although not the fact that it needs to be changed. Nevertheless, we really need to measure rain forests more systematically and clearly. "

US look

“Natural resources specialists must see forests up to the resolution of perturbations — a scale that shows how much forest each park, building, or farm is worth,” says Joseph Kellndorfer of the Woods Hole Research Center (WHRC). His team recently managed to reach such a resolution by releasing the National Biomass and Carbon Dataset National Biomass and Carbon Database (NBCD) in April 2011





Currently, NBCD is the forest biomass map of the highest resolution ever recorded. Scientists at the Woods Hole Research Center made it by combining satellite and high-precision ground-based measurements. (Map by Robert Simmon, based on data from the Woods Hole Research Center.)





“The information we provide is on a managerial scale,” notes Kellndorfer. The forests in the United States, as well as their carbon content, are marked up to 30 meters, or about 10 pixels per hectare of land. “This data is a comprehensive view of forest structure and carbon stocks, and they provide an important basis for assessing future changes.”

For 6 years, Kellndorfer, Ein Walker and their Woods Hole team collaborated with the US Forest Service and the US Geological Survey to compile a national forest map based on observations of space radars, optical sensors, computer simulations, and a vast array of ground-based measurements. They divided the country into 66 cartographic zones and, as a result, built on the map 265 million segments of the surface of America. Estimated Kelnsdorfer, the base contains measurements of about 5 million trees.

Scientists began research with data from the Shuttle Radar Topography Mission, which was launched on the Endeavor shuttle in 2000. Using this radar, the USGS and NASA's Jet Propulsion Laboratory built topographic maps of almost the entire surface of the Earth from 60 degrees North Latitude to 60 degrees South.

By 2005, Kellndorfer had finished deciphering the signals (scattering surfaces) of electromagnetic waves received by the radar — data showing the height of the vegetation. Subtracting from the height of the tops of trees, the height of the earth above sea level, scientists were able to estimate the height of plants, trees and shrubs covering the surface of the Earth.

These numbers were just the beginning. The Kellndorfer team compared the data with the National Land Cover Database, which was constructed from satellite images taken by Landsat. They studied the biology and geology of images. How does the rise above sea level affect the height and thickness of trees? What can and cannot grow at specific heights?

The last piece of the puzzle was data from the ground. Kellndorfer thanks Elizabeth LaPoint and her colleagues from the Forest Inventory and Analysis program of the US Forest Service for them. The federal foresters own the census of all the trees in the country and keep it up to date for each of the 6,000 acres of forest, taking measurements of trees at each site at least once every 5 years.

These data, however, are not publicly available and neither Kellndorfer nor anyone else in the Service can study them. Such rules were introduced to preserve the integrity of the database and protect the rights of private owners. So the Woods Hole team prepared thousands of individual data sets of 15–20 variables so that LaPoint could compare from its forest registry.





NBCD is divided into 66 regions. The zone corresponding to the northwest Pacific coast has the highest biomass density in the United States. (Map by Robert Simmon, based on data from the Woods Hole Research Center.)



In the end, the team was able to construct a map that was more accurate and of higher resolution than any previously created. The map shows the chess structure of logging in the old logging sites in the northwest and the carefully cultivated forest farms in the Southeast. In the Midwest, trees accompany rivers and serve as boundaries between farms. Also, forests come to life on the ground, previously treated for crops. On the Atlantic coast and in New England, lands cleared of forests during the time of the formation of the USA are now again covered with forests. Although among the forest and saved a lot of urban settlements.





At full resolution, the NBCD scale allows you to view individual areas of logging. (Map by Robert Simmon, based on data from the Woods Hole Research Center.)



“Forests are a key element of human activity,” says Kellndorfer. “So we need to know how many of them we have and where in order to manage and use them qualitatively. This map is another tool to look at our priceless property. ”

Building new ways of measuring

Lidar, radar, optical photography, ground studies, computer models - all give slightly different answers to the same question. Three different teams created three different forest carbon maps in 15 months. Groups at Stanford, the European Space Agency, Brazil, the US Forest Service and dozens of other agencies are trying to answer the same questions. Sometimes as allies, sometimes as rivals.

Looking from the outside, it seems that some of these studies are redundant. But parallel approaches and competitiveness have always led to innovation and a deeper understanding.





(NASA photograph courtesy Jon Ranson, GSFC.)

In the photo: David Harding (left), Charles Gateby (right) and Raphael Rincon (behind) - three scientists from the Eco 3D field campaign. Each of the researchers was responsible for his instrument. The work on understanding the world's forests is carried out by a multitude of groups, each of which considers a task from its own side.



“It’s like a cancer study.” Many different laboratories in different countries solve the same problem, ”says John Ranson. “Everyone looks from his side and has his own methodology. Groups cooperate as much as they can, collecting data and extracting from them what is possible. In the end, research complements each other and moves science as a whole. ”

The ultimate goal is a single standardized map of forest heights and carbon stocks on all continents at one point in time. And this map must be updated in order for a person to change and update the planet.

“We have something to grasp on in studying the world's forests, but so far there is no clear sense of the structure or dynamics of change,” says Steve Running, a member of the International Climate Change Group. We need the best way to measure global carbon stocks annually. We need to know how the state of things changes with time due to fires, the emergence of a new forest, drainage of land and deforestation. ”

“How do we cover the whole world,” adds Running. “And measure it every two to three years, because this is exactly what science needs?”

The number of study opportunities to date has decreased. In 2009, he completed his work ICESat. His successor, ICESat II will be launched in 2016, but not the fact that he will be able to see forests as well as his predecessor. Synthetic aperture radars used for the Shuttle Radar Topography Mission provided a global image of the terrestrial landscape at the start of the “nil”, but the Shuttle program was retired in July 2011. Some of these technologies could provide worldwide coverage of the structure of the world's forests every year. being launched in the form of a space station, or satellite.

Many forest researchers and environmentalists were hoping for a space program proposed many years ago and recommended by the National Research Council in 2007 - Deformation, Ecosystem, Structure, and Dynamics of Ice satellite. DESDynl had to combine radar and lidar technologies in order to get a three-dimensional picture of the forests and the carbon stock in them. But this program was postponed indefinitely in the spring of 2011, when the US government cut the budget. Researchers are now looking for other ways to send equipment into orbit.





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Links

1. AsiaOne News (2011, August 7) Googling Earth to fight graft. Accessed August 30, 2011.
2. Bonan, GB (2008, June 13) Forests and Climate Change: Forcings, Feedbacks, and the Climate Benefits of Forests. Science 320, 1444.
3. Environmental Protection Agency (2010, June 22) Carbon Sequestration in Agriculture and Forestry: Frequent Questions. Accessed September 18, 2011.
4. Lefsky, MA (2010) A global forest canopy height map from the Moderate Resolution Imaging Spectroradiometer and the Geoscience Laser Altimeter System. Geophysical Research Letters, 37, L15401.
5. Pan, Y., Birdsey, R., et al (2011, July 14) A Large and Persistent Carbon Sink in the World's Forests. Science 333, 988–993.
6. Running, SW, Nemani, RR, Townshend, JRG, and Baldocchi, DD (2009) Next-Generation Terrestrial Carbon Monitoring (PDF). AGU Geophysical Monograph Series 183: Carbon Sequestration and Its Role in the Global Carbon Cycle, 49–69.
7. Ryan, MG (2008, June 4) Forests and Carbon Storage. US Department of Agriculture, Forest Service, Climate Change Resource Center. Accessed September 18, 2011.
8. Saatchi, SS (2011, June 14) Benchmark map of forest carbon stocks in tropical regions across three continents. Proceedings of the National Academy of Sciences, Vol. 108, No. 24, 9899–9904.
9. Space News (2011, February 25) Two High-priority Climate Missions Dropped from NASA's Budget Plans. Accessed September 28, 2011.
10. Tollefson, J. (2009, December 15) Satellites beam in biomass estimates.Nature 462, 834–835.

Materials

1. Jet Propulsion Laboratory (2011) Terrestrial Carbon Cycle Research. Accessed September 15, 2011.
2. Woods Hole Research Center (2011) National Biomass and Carbon Dataset. Accessed September 15, 2011.

1. NASA Earth Observatory (2011) Notes from the Field: Eco3D—Exploring the Third Dimension of Forest Carbon. Accessed September 15, 2011.
2. NASA Earth Observatory (2011, June 16) The Carbon Cycle. Accessed September 15, 2011.
3. NASA Scientific Visualization Studio (2011, April 8) Intro to Lidar 3D. Accessed January 4, 2012.
4. NASA Earth Observatory (2010, July 22) Forest Canopy Heights Across the United States. Accessed September 15, 2011.
5. NASA Earth Observatory (2008, February 2) Tree Canopy Height from 1650 to 1992. Accessed September 15, 2011.
6. NASA Earth Observatory (2008, February 1) Ancient Forest to Modern City. Accessed September 15, 2011.