You know that scientists do research to learn new things. They also do research to test what they believe to be true. Scientists may also do research to improve scientific methods. New types of technology are available all of the time. You can see changes in technology in the way that cell phones continue to be improved. Research that explores the use of new technologies helps all scientists to use the new technologies. Scientists use these technologies to tackle important questions in new ways that help us better understand our planet.

In this research, the scientists combined three different ways of gathering information: an older, traditional method along with two new technologies. The older method involved going out into the forest to collect information by hand. The two new technologies involved airplanes, satellites, and computers. By combining these three methods of collecting information, the scientists were able to produce new information. This new information increases our understanding about 1 million hectares of land– an area about the size of Connecticut. This research enabled the scientists to test a new scientific method that will help other scientists do research about large, diverse areas of forest.

Every tree contains carbon. If you remove the liquids from a tree, about one-half its weight is carbon. When trees are growing, they help to combat climate change by absorbing carbon from the atmosphere. Trees store carbon in their wood. When trees are cut and burned, the carbon in them is released back into the atmosphere in the form of carbon dioxide (CO2 ). There, it contributes to climate change by heating our planet. It is, therefore, important to protect our forests worldwide. When forests are left standing and protected, their carbon is kept out of the atmosphere and the forests are able to collect and store even more carbon.

Scientists want to know how much carbon our forests contain. Knowing the amount of carbon is the only way to keep track of any change over time. In a way, tracking the amount of carbon is like keeping track of your own weight. If you never weighed yourself, it would be hard to say for sure whether or how much weight you were gaining or losing. When you think about the amount of carbon in forests, you can see what a big job this tracking is. Forests cover a lot of land and are different in terms of their structure and types of species that live there. Scientists need to use new tools and technologies, therefore, to help them estimate how much carbon large areas of forests contain.

You may have heard about carbon trading and carbon credits. These phrases refer to programs aimed at reducing carbon dioxide emissions to the atmosphere. These programs involve balancing an amount of carbon emissions with activities that reduce an equal amount of emissions. If someone were driving across the United States, for example, his or her car would emit a certain amount of carbon dioxide during the trip. To make up for these emissions, the driver might voluntarily contribute money to an organization that protects forests. To balance the car’s emissions, the driver would have to know three things: (1) how much carbon dioxide the car would emit during the trip, (2) how much forest land would contain that same amount of carbon, and (3) how much money it would take to help protect that much forest land.

In this study, the scientists were interested in the second item. They wanted to test a method of calculating the amount of carbon stored by plants across a large area of land. They chose the island of Hawai‘i to test their method. Hawai‘i is the largest island in the Hawaiian Islands (figure 1).

It contains 1,000,000 hectares. Hawai‘i has volcanoes, forests, pastures, grasslands, developed areas, and many types of ecosystems and land cover (figure 2). Hawai‘i is one of the most ecologically diverse places on Earth. It has areas with high rainfall and also deserts with low rainfall. It has areas at sea level and at very high elevations. Each of these areas contain a different amount of carbon. Forests, for example, hold more carbon than grasslands.

In the past, people working directly on the land estimated the amount of carbon stored in plants. This method, although fairly accurate for the actual trees being measured, was expensive and took a long time to get enough samples. In addition, this method could estimate only the amount of carbon in small areas of land. This information was not enough to understand forests across large areas. Remember that there is now a need to understand how much carbon large areas of forest and other types of land cover store. To meet this need, the scientists decided to combine the old method with new technologies.

The scientists used new laser technology called Light Detection and Ranging (LiDAR). The scientists also used satellite technology that estimates how much land has certain types of vegetation. Combining old and new methods enabled the scientists to estimate the amount of carbon stored in different types of forests. They could then create a carbon map of the whole island of Hawai‘i.

The scientists used four steps to test their method for carbon mapping. First, they used existing maps of the land cover of Hawai‘i. People working on the land created some of these existing maps, and satellites and computers created others (figures 4 and 5).

Using these maps, the scientists identified the land cover of different areas. Using information from the satellite and a computer program, they identified areas that had forests and areas with no forests or those that might have been deforested (figure 6).

Have you used Google Earth to see objects on Earth close up? If you have, you can see how the scientists identified conditions of forests and other areas on Hawai’i using satellite photos. Google Earth uses Landsat photos, just like the scientists did.

The scientists then used LiDAR to better understand the vertical structure of the plants and trees (figure 7). About 25 percent of the island was sampled. The areas sampled included a wide variety of land cover and ecosystems.

The third step was to identify areas on land to study in person. The scientists identified 126 areas for sampling where they established plots. Each plot was an imaginary circle with a radius of 30 meters. Each of these 126 plots had also been sampled using LiDAR. In each plot, the scientists identified and measured all trees that were 5 centimeters or larger diameter at breast height (DBH) (see sidebar). The scientists then used existing equations that related DBH to the amount of carbon in the tree. For example, trees with a DBH of 5 to7 centimeters were already known to contain a certain amount of carbon. In this way, the scientists were able to estimate the amount of carbon contained in each of the 126 plots.

In Step 4, the scientists looked at the LiDAR information on vertical structure in each of the 126 plots. They compared this information with their direct measurements of the plants’ carbon content. The scientists discovered that the amount of carbon in each plot was related to the center of the vertical height of the trees. If the scientists could calculate the center of the vertical height of any forested area in Hawai‘i, they could estimate the amount of carbon being held in that area. Plots with taller trees, for example, held more carbon. In other words, the scientists found that by using LiDAR to identify the average height of the trees in an area, they could accurately estimate the amount of carbon stored by plants in that area.

The scientists then combined the vegetation maps that they used in Step 1 with the carbon estimates made using LiDAR in Step 4. If they identified an area as being deforested or degraded (Step 1), they reduced their estimate of the amount of carbon in that area. This method enabled them to apply the carbon estimates to each of the land cover areas in the existing maps. By applying carbon estimates to each area of land, they were able to create a carbon map of Hawai‘i.

The scientists discovered that the amount of carbon in an area was related to the type of soil and climate conditions in the area. Areas with older Hawaiian soils contained more carbon than areas with young soils. Areas of Hawai‘i with high rainfall contained more carbon than areas with lower rainfall. The scientists also found dry areas, whether they were warm or cool, contained smaller amounts of carbon (figure 9).

The scientists discovered that areas with little or no forest land contained less carbon than forested areas. Forests that had been planted in the 1930s in areas where rainfall was plentiful contained the highest amount of carbon.

The scientists concluded that the use of LiDAR to estimate carbon is as accurate as making the estimates in person. Because LiDAR can be used over a large area, the cost of using LiDAR is much less than trying to make inperson estimates over the same large area. Using LiDAR, moreover, enables scientists to make carbon estimates in remote areas people would have a hard time visiting.

The scientists also concluded that after they made an initial carbon map, they can easily update it using Landsat photographs that show changes in land cover over time. In particular, Landsat photographs will show the locations of new deforestation and degradation as well as new forest growth. Existing carbon maps can be updated to show the decrease or increase in carbon storage due to these conditions.