# Presentation: 561838

## Slide 1

## Land ecosystems cover nearly 30% of the Earth’s surface. The land surface changes over days, seasons, decades, and longer. Vegetation boundaries shift, cities grow, rain forests and farm lands shrink, amounts of trace chemicals in the air increase and decrease, rivers flood, forests burn, and volcanoes erupt. Activities of the growing human population cause or influence many of these changes.

## Space provides an excellent vantage point from which to observe and record land surface changes, especially at a global scale. NASA has embarked on an ambitious effort to measure the effects of changes on our planet and to understand the roles that human activities play in them. A suite of Earth-observing satellites measures different aspects of the land and builds a global picture of change, one location at a time.

## These images show Santa Ana wind-driven fires burning in Southern California on October 22, 2007. The natural-color image at bottom shows smoke plumes being blown west over the Pacific Ocean. The small red boxes pinpoint the actual fire locations. The top right image highlights the resulting burn scars, and shows how widespread the fires were at that time. This image combines visible and infrared light in such a way as to allow burned areas (brick red) to stand out from unburned vegetation (bright green). Desert or semi-arid landscapes are beige, dense urban areas are gray, and water is dark blue. Two of the October fires, the Witch and Harris Fires, were among the top 20 largest fires recorded since the 1930s.

## These five images demonstrate land use change in five major cities around the world. The base images were acquired by satellite on the dates indicated, with vegetation represented in green, water in dark blue/black, and bare ground in purple. The bright yellow map overlaid on each image indicates the extent of urban development around 1990. Orange illustrates the amount of additional urban growth between 1990 and 2000.

## The images above show the location of the Three Gorges Dam (far right) on China’s Yangtze River, the longest river in Asia. Evident here are the changes to the landscape caused by the construction. The image on the left was acquired on April 17, 1987, well before the dam project had begun. The right-hand image was acquired on November 7, 2006 after the completion of the dam’s main wall. Combined satellite imagery and computer models seem to indicate that the creation of the huge reservoir of water behind the dam has altered precipitation patterns in the area, decreasing rainfall in the immediate vicinity of the dam, while increasing it farther away.

## The globe above shows the difference in land surface temperature between the period of January 1-24, 2006 and average January temperatures for the period of 2001-2005. Note here that the eastern half of the U.S. was much warmer than average during January 2006. At the same time, Alaska, southern Africa, western Australia, and much of the Russian Federation were experiencing particularly cool temperatures relative to the average. These satellite measurements indicate heat emitted by the Earth’s surface. This type of information can inform farmers of crop temperature, making it possible to better estimate water requirements and crop yields.

## The images at left show seasonal variation in foliage color between summer (July 17, 2006) and fall (October 30, 2006) in the mid-Atlantic and northeastern U.S. In the fall image (lower left), note the difference in color along the highest ridges in the Appalachian Mountain chain (see inset below). The deep green patches that remain among the otherwise-orange vegetation indicate the presence of evergreen trees—hemlock and red spruce—that grow in higher concentrations along these two- to four-thousand-foot-high ridge lines.

## NASA’s Earth Observing System scientists study the Earth as a system in order to be able to predict change. All aspects of the system are actively interlinked. For example, exchanges of energy and moisture, and chemicals such as carbon dioxide, methane, nitrogen oxides, and hydrocarbons take place between the vegetation and the atmosphere. 

## These exchanges are influenced by properties of the land, such as the underlying soils, the overlying vegetation, and land management practices, so understanding land cover changes helps us to understand the whole Earth system. Building a global picture of changes on the land, the Earth Observing System provides data on vegetation patterns, desertification, deforestation, the occurrence of fires, floods, volcanoes, and more.

## Slide 11

## A remarkable transformation has taken place in the city of Dubai in the United Arab Emirates over the past two decades. Dubai has emerged as a major metropolis and tourist destination and is home to 1.2 million people.  Much of the new development is taking place on several man-made islands called the Palm Islands—so-named because they have been shaped like palm trees. The islands are the largest land reclamation project in the world and, when complete, will be the world’s largest artificial islands. They stand as a reminder that sometimes, human alterations to the landscape can have a positive impact on society. 

- The two images shown here demonstrate just how much Dubai has changed since 1973. On January 22, 1973 (upper left), there was little evidence of human engineering of any kind. The lack of roads is evident. Very little development appears to exist along the coast. Empty sand stretches southwestward from the inlet in image center. In contrast, by October 11, 2006 (lower right), four artificial islands in various stages of development are clearly visible—note that The World site will look like a world map when it is complete—as well as plenty of evidence of human alterations to the landscape on the mainland.

## Human beings have an insatiable appetite for consumption. It seems that everywhere we go, we have a way of depleting the natural environment—clearing forests, stripping the soil of nutrients, polluting streams, and so forth. Humans are particularly dependent on Earth’s plant life. Plants provide the basis for all food, and much of our fuel and construction material, etc. There is rising concern as to whether the planet will be able to keep up with the ever-growing demands that society places upon Earth’s limited resources. 

- Scientists are using satellite observations to help answer this question. Shown at left is a global map of annual average net primary production—the amount of plant material (trunks, leaves, roots, branches) produced in the course of a year and available in a location. Not surprisingly, the greatest production is found in the tropics, where dense forests filled with many layers of plants thrive.

## This map makes it clear that in many areas, human consumption far exceeds what the local environment can provide.  This is true for densely populated countries like India and China. It’s also true for smaller countries in areas with naturally low production, such as Saudi Arabia, and even for productive areas like the eastern United States and Europe, where levels of per-person consumption are extremely high.

- Scientists speculate that the ratio of human consumption to regional net primary productivity could be an indicator of locations that are particularly vulnerable to supply disruptions, for example, as a result of natural disasters or civil unrest. Combined with models of the impacts of climate change, these studies could also help countries predict the biosphere’s ability—or inability—to sustain their population’s consumption levels in the future.

## One of the more interesting applications that NASA scientists have developed in recent years is the ability to use Earth observation data to study the spread of infectious diseases. They’ve looked at several diseases, such as Ebola and Rift Valley Fever, known to be more likely to spread under certain environmental conditions. Satellites are ideally suited to observe these conditions months in advance.

- Temperature and precipitation are environmental factors thought to aid in the spread of these diseases. As vegetation responds to both of these factors, satellites provide information to help study their role in disease outbreaks with even greater accuracy, by measuring the Normalized Difference Vegetation Index (NDVI) as a substitute for vegetation greenness.

## This map of Africa, which shows percentage tree cover, highlights Ebola outbreaks from several decades. A pattern that becomes clear is that Ebola outbreaks tend to occur toward the edge of a forest. When we further look at the temporal plots of NDVI for five selected locations, we see that despite a wide range of locations, all outbreaks (noted as circles on each graph) tend to occur toward the end of the rainy season, or after a seasonal peak in NDVI.

## Slide 17

## U C L

- U C L

## Slide 19

## Aqua

**Aqua**
- The Aqua mission, launched in May 2002, carries six instruments, four of which provide significant contributions to land studies. These four are MODIS, also on the Terra satellite (see above), the Atmospheric Infrared Sounder (AIRS) and its companion Advanced Microwave Sounding Unit (AMSU), and the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E). AIRS/AMSU data can be used for calculating land surface temperature, while AMSR-E data have been used in detecting and analyzing extreme flood events and in obtaining indications of soil moisture.

## LDCM

- The Landsat Data Continuity Mission (LDCM) is the successor to Landsat 7. It is scheduled for launch after July 2011. LDCM will detect both natural and man-made changes on the surface of the Earth. These continuing observations are key in the study of land use and land cover change, global climate research, and polar studies.
**SMAP**
- The Soil Moisture Active-Passive mission will measure surface soil moisture, which is useful in improving our ability to forecast weather, flood and drought events, and to predict agricultural productivity and climate change. It’s proposed launch date is between 2010 and 2013.
**DESDynI**
- The Deformation, Ecosystem Structure and Dynamics of Ice mission will help determine the potential for earthquakes, volcanic eruptions, and landslides. It will also be useful in monitoring the effects of land use on species habitats and the carbon budget, as well as helping to better study the responses of the Earth’s ice sheets to climate change and resulting impacts on global sea level.

## Slide 22