Satellites afford excellent means to monitor on-going and potential ecological threats and damage, as well as long term after effects, to the Earth’s natural surface and to areas relevant to human activities. Sometimes, ongoing ecological problems can be watched in near-real time using both high resolution and geostationary satellites. This is true for assessing the damage done to wetlands, shorelines, and forests hit by strong hurricanes. Much obvious damage is imposed on vegetation by forest fires and grassland burns. Also, normally very easy to see are the destruction and deposits associated with sand storms. Dust storms brought about by nature but sometimes made more severe because of human land practices can affect large regions. Oil spills constitute another ecological catastrophe that often is detectable in Landsat-type imagery and under favorable conditions in radar scenes. Damage deliberately attributed to human decisions includes strip mining. Illustrative examples are given.
Perhaps the most devastating natural event that affects both human infrastructure and natural landscape and vegetation is the massive storms called "hurricanes" or "typhoons". We show examples of these on page 14-10. Here we will show just a few illustrative examples of the kinds of damage that result. Hurricane Lili occurred in October of1996, starting in the warm Atlantic, passing over the Bahamas and other islands, causing considerable destruction of natural features as well as property.
Here is a satellite view of labeled damage on the small Bahaman island of San Salvador:
Ivan, in September 2004, did similar damage to Florida coastline dunes and vegetation
Trees are very vulnerable to being toppled by hurricane-force winds. Here are trees in New England blown over during a 1938 hurricane (they weren't given names then):
Landsat and other satellites are very effective in characterizing ecological habitats and in monitoring any changes that threaten plant or animal life, especially species considered endangered or subject to undesirable influences. One of the most famous habitat focal points in recent years is the battle between environmentalists and the lumber industry over what timbering, such as the clear-cutting considered in Section 2, is doing to the very specialized conditions in which the Spotted Owl (shown below) prefers:
This species favors dense, particularly first growth, fir forests. Although not yet rare on the West Coast, the owl is losing some of its prime habitat. At this time, there is a partial moratorium on harvesting certain types of forest ecology that support the Spotted Owl. The U.S. Forest Service is using Landsat in two ways: 1) to produce a basemap (shown below with the dark green being Spotted Owl territory), and 2) to ensure that these areas are not subjected to illegal clearcutting. Here is a classification of a large tract in northwest Oregon that singles out areas favored by the owl:
Landsat and other space observation systems efficiently monitor transient ecological maladies such as insect defoliation (as you saw in the Pennsylvania "Exam" at the end of Section 1). Drawing upon your recollections from that exam, in which you learned to pick out gypsy moth defoliation, you should have little trouble in spotting the defoliation telltales in this subscene enlarged from the Landsat-1 MSS image that includes Harrisburg (just to the south):
On page 3-5a, we examined in detail a widespread defoliation threat to pines in the western U.S. One more example: The Gall Wasp, from Asia, has reached the Hawaiian Islands by "hitching a ride" on ships. It has a 'taste' for the coral-colored leaves of the Wiliwili tree (sp.: Erythrina) which is found on several of the big islands. In this Landsat image of Maui, yellowish areas are defoliated Wiliwili trees. Both short- and long-term imagery, from various satellites, afford a means of observing the spread of wasp damage and aid in selecting areas for spraying.
Many ecological problems (some are actual disasters) occur within very short time frames. A prime example is vegetation fires in grasslands and forests. Monitoring from space is especially well suited to watching these fires as they occur and after they are extinguished to gauge their effects. Both those set purposely for beneficial purposes and those which are unwanted are proper subjects of this surveillance.
In the first category, controlled burning (including the cut and slash approach to management of crops and grasslands) on a grand scale is especially commonplace in the African savannah. We show first a pair of images made by the MODIS Airborne Simulator (MAS) (see Section 16); the one on the left simulates natural color and on the right depicts the ability of using longer wavelength infrared to penetrate the smoke to see the actual flames. In September, 2000 much of south-central Africa was covered by major controlled fires. The image below was made using a combination of registered imagery from the NOAA-14 AVHRR and the TOMS sensor (see page 14-9). In this next higher resolution image made by Aqua's MODIS on May 6, 2004, more than 4000 individual control-burn brush fires in the Democratic Republic of Congo and Angola are underway (not all visible in the image below but countable in a transparency made from this source): This mode of agricultural management is widespread during the dry season in Africa, but peaks at different times in various parts of the continent. MODIS has taken a series of observations at 2-week intervals during 2005, with these results (the solid reds and yellows indicate regions of widespread burning, being subcontinental in scope):
Forest fires usually burn for a few days to several weeks (especially in isolated areas) until brought under control. A fire in the Fishlake National Forest near Beaver, Utah (about 60 km [40 miles] ESE of the White-Mountain scene you will examine in Section 5), was imaged by the NOAA-9 AVHRR (1 km ground resolution), on June 17, 1996.
This false color composite was made by assigning the channel (a synonym for band) 1 image to red, channel 2 to green, and channel 3 to blue. In this version, the grayish smoke shows as yellow and the fire, at the base of the smoke column, appears as bright blue. Major fires are commonly imaged by meteorological and land-observing satellites, and the extent of the burn damage is easily assessed afterwards by the dark patterns in the visible bands. These dark patterns are usually evident as bright patches in thermal imagery because of the blackbody effect (see page 9-1).
The great wildfires of 2002 in Arizona, Colorado, and elsewhere in the western U.S. were examined in the Overview. In 2000, a major fire in New Mexico consumed more than 46000 acres and destroyed 260 homes in Los Alamos, the town supporting activities at the Los Alamos National Laboratory where technology dealing with uses of nuclear energy (including the nuclear bomb which was developed there in 1945) is the principal industry. Landsat 7 captured spectacular views of this fire. The image below was made from TM Band 2 = blue; Band 4 = green; and thermal Band 6 = red. The dark red spots in the resulting scene are actual flames or very hot burn areas.
Fire outbreaks continued through the summer of 2000 when at one time more than a million acres in 7 western states made this the worst forest fire season in more than 50 years. In mid- to late-August, the most widespread burning was in Montana. This Landsat TM scene shows mountainous terrain whose forests are on fire at several places; the already burned areas are in red.
Much of the U.S. has been experiencing mild to severe droughts since the late 1990s. Satellites can not only sense fires that break out but can monitor conditions that indicate the likelihood of future fires. The Fire Potential Index (FPI)uses data from meteorological and other satellites to measure Soil Moisture, which is a predictive indicator of stages of dryness in western forested or grasslands areas. Most fires there start from lightning strikes; some are manmade (carelessness or deliberately set. The calculated FPI for a period between July 20 and 27, 2000 is shown below:
Forest fires are common targets of opportunity for astronauts and cosmonauts during their photo sessions because these are usually so obvious when seen from space. Here are fires in the tropical north of Australia:
On a wider scale of view, forest fires in three separate areas, one in Borneo, north of Java, and two in Sumatra, in 1997 were imaged by NOAA-14 (at a resolution of 4 km [2.5 miles]), as seen here:
Air pollution on a grand scale is often easily visible from space. An imposing example is the mixture of smoke and smog created by fires spread over many islands in Indonesia. Using imagery acquired by TOMS, and set against a backdrop developed from NOAA data, a huge smoke plume (white), mixed with smog (colors represent variations in ozone amounts) is seen to be heading westward from the islands across the Indian Ocean. Indonesia is a country that practices slash and burn. This is evident in this MODIS image, in which some fires are natural, others manmade:
China has had many problems with widespread pollution owing to its rapid transition to heavy industry and to increased automobile usage over much of the country. This next image, taken by SeaWIFS (page 14-13), shows a brown haze covering much of northeastern China to the extent that land surface features have been blotted out. Many of China's huge cities, such as Shenzhen and Beijing, are becoming notably unhealthy for their inhabitants. Pollution from China spreads over much of SE Asia and Japan, and has been traced as far away as western North America.
Natural air pollution from intense dust storms also besets China from time to time, especially when winds remove fine materials from the Sinkiang and Mongolian deserts. This MISR image pair shows a part of eastern China near the Korean border; on the left, a relatively clear day and on the right the almost total obscuration from a thick cloud of dust:
A major dust storm, coming from the Gobi Desert, passed over much of northeast China in mid-March of 2006. Here it is in an Aura MODIS image taken on March 9. Some snow that fell during this passage actually had a yellowish tone owing to intermixing with the dust. Beneath the image are three views of its progress (follow the red patch), in which Aura' OMI (Ozone Monitoring Instrument) allows variations in cloud densities to be assigned colors.
Dust storms are also common off the Sahara Desert of Africa, as is displayed by this pair of images taken two days apart:
This Terra image shows a strong dust storm on November 11, 2006 coming off the western Sahara and extending out to the Canary Islands.
Sometimes strong sand storms can be imaged in the act of their formation and movement, especially in the deserts. Astronauts aboard the International Space Station caught this storm as it advanced on February 15, 2004 across the desert of Qatar along the Gulf of Arabia.
Another example of air pollution was detected just two months after ERTS-1 was launched. The area affected included Goddard Space Flight Center the operational home of the ERTS-1 satellite. On a particular day in September the writer remembers a severe smog (pollution) alert for the Washington and Baltimore region. Later, in checking through some of that early imagery, I found the image shown next that dramatically revealed the extent of pollution on that day. The area shown is east of these cities in the Upper DelMarVa peninsula (mainly Maryland's Eastern Shore); the loss of red is due to the thick blanket of smoke (in white, with light yellowish tint) above the dominantly agricultural and forested terrain.
A more localized form of air pollution derives from SO2 and other gases released from smokestacks onboard ocean vessels such as freighters. This condenses along with water vapor to form cloud trails similar to those made by jet airliners. Here is such a phenomenon seen over the Pacific Ocean:
Turning now to water quality issues: Two telling examples show water pollution in remote sensing images. The image below, made by the Coastal Zone Color Scanner (CZCS) on Nimbus 7 (see page 14-13), includes the shallow shelf region of the Atlantic Ocean in the Long Island Bight, south of New York City. For decades, a train of barges has carried waste materials (euphemism for garbage) several times a week to an offshore dumping site. The barges move in a zig-zag pattern that leaves a distinctive curlicue pattern of pollution, which is readily apparent (the orange pattern in the water) in this color image. Another dreaded ocean contaminant is oil spills. Oil is noted for "calming the waters", i.e., reducing the degree of wave disturbance, making it visible in certain spectral bands. Multiple oil leaks in the Arabian Sea, west of Bombay, India, are obvious in the SIR-C radar image below. Their darkness is not solely due to black oil color involving light absorption but also to the decreased backscatter of the radar beam (see Section 8 for the principles). Radar imagery, especially in the black and white mode, is very effective at locating and monitoring oil spills over their full extents. This next image, made by the radar unit on Envisat, shows how radar graphically highlights the large oil spill resulting from the breakup of the oil tanker Prestige in late November, 2002. Most of its cargo of 20 million barrels went down with the ship as it sank into deep waters. But 1.5 million barrels of oil eventually reached the northwest corner of Spain, contaminating almost 300 km (200 miles) of beach. Here is a radar image taken soon after the spill leaked out. 3-16: Can oil spills be detected in Landsat imagery? ANSWER Oil can also reach marine surfaces from so-called "oil seeps", which are natural effusions of oil from fractures underlying the ocean floor. Off Santa Barbara (California) is a persistent natural "spill" shown here as an ERS-1 radar image:
With the advent of high resolution satellites, much more information is now available over short turnaround times above major oil spills. One occured in the Aleutians off Unalaska in mid-December, 2004. A tanker split in half, leaking 10s of thousands of gallons of crude into offshore waters. The boat wreakage and oil-coated waters were imaged by Quickbird:
Other types of water pollution can be detected from space. One of the first demonstrations of this is the example of waste pulp and hot water from a paper mill being dumped (illegally) into Lake Champlain from a New York site. Its effect was to reduce water wave action. The ERTS-1 subscene shown below was used in a legal court case in which a judgment against the mill owners was won by the State of Vermont. This space imagery application was given much attention in the newspapers.
Lakes are also subject to natural variations which affect their "health" and quality. Phytoplankton are algal-like plant that can thrive in freshwater lakes, changing in quantity with the seasons. The Modular Optoelectronic Scanner (MOS) on India's IRS-P3 satellite was used to monitor amounts of phytoplankton in Lake Constanz (also known as the Boden See) along the Swiss-Bavarian border (in northeast Switzerland) for several years, as seen in this succession of images (time-series) from May, 1996 through February, 1998:
One of the major concerns about humans' destruction of the environment is the alarming reduction in wetlands (see page 3-5) - marshes within landmasses, particularly those associated with rivers or near the coasts, that are ecological habitats for various plant species and many specialized animals (particularly birds) adapted to living in these watery conditions. Extensive wetlands tracts occur at ocean/land boundaries. One of the best known in the U.S. is wetlands and bayous along the Delta country where the Mississippi River meets the Gulf of Mexico, as seen here:
Another major wetlands is found behind the Outer Banks of North Carolina (see page 17-4 for an image that includes nearly all of this landform) which is a classic example of a regional offshore bar. This astronaut photo shows the water bodies behind the oceanic sand bar (Bodie Island). Note that a second, older bar (which once was the main barrier island) lies to the west; agriculture has taken hold on this land as wind has removed some of the sand leaving silty soil. The widest expanse of wetlands is the area around the words "barge wake":
">
Wetlands are often deliberately destroyed to recover land for agricultural development or for home building. One of the most famous wetlands - the marshes of Mesopotamia, in Iran and Iraq which were a key factor in the rise of cultured peoples in the "Cradle of Civilizations" - has undergone drastic draining and dessication in just the last 30 years. Below are montages made from Landsat imagery in 1972 (top) and a 1997 RESURs image (bottom) of an area where the Tigris and Euphrates rivers meet around Shatt-al-Arab. Damming of the rivers and deliberate diversion of their waters have reduced the marshlands that once covered more than 20000 sq. miles to now less than 4000 sq. miles.
This land reclamation was done largely to increase available land use for Iraqi development around Basra and the port of Umm Qasr where oil from the Rumaila fields is shipped to tankers plying the Persian Gulf. When the second Gulf War took place, it was feared that the Iraqi forces would blow up dams upstream to reflood the marshes, possibly affecting populated areas. This did not happen. Here is a satellite view of central Basra, Iraq's second city (about 1,000,000 people):
After the war, and with a new Iraqi government in place, the decision was made to restore the Mesopotamian wetlands near Basra, as this should also improve ecological conditions upstream. These two MODIS images tell the story: In 2002, the wetlands were nearly gone but by 2007 they had been revitalized to conditions prevalent at the start of Saddam Hussein's policy of draining the marshes:
Similar to our clearcutting examples already examined above, satellite systems can follow long term changes in resource use, such as strip mining and the progress of land reclamation (as you noted in the Pennsylvania case study in the first Exam). Strip mines often produce a very distinctive pattern, as in this aerial photo that shows the bench method of strip mining in a near-surface metallic ore extraction operation.
In standard false color images strip mines in coal are often indicated by a distinct signature (bluish to bluish-black) that represents the barren exposed surfaces with a residual covering of coal lumps and dusts causing the ground to appear dark. This is the case in this Landsat subscene in the anthracite belt of northeast Pennsylvania (part of the image shows lighter reds indicating some reclamation): This is evident again in the image below, which shows strip scars (light to medium blue), replanted areas (red stripes), and farmland in the coal measures of western Maryland (Allegheny Plateau). The image was made by the Linear Pushbroom Radiometer (LAPR) developed at Goddard Space Flight Center as a prototype to test the CCD array concept and flown on a NASA aircraft. Satellite imagery is particularly good at monitoring changes over years in the progress of strip mining - both in expanding development and in reclamation. Note the differences between 1987 and 2002 in the Hobet mine on a plateau mountaintop in West Virginia:
As a transition image to the next Section, the TM scene below shows an urban area near Leipzig in Germany, surrounded by numerous large fields, both fallow and with diverse crops, and several large white areas (those being clouds have associated shadows) which are the unfilled and poorly reclaimed scars of major surface pits from which soft coal was dug out for heating and power production in the past.
Elsewhere in Germany, in North Rhine Westphalia, this ASTER natural color image shows three very large strip mines:
We will illustrate other agricultural, forestry and ecological applications in this Tutorial (several appear in Sections 6, 13, 16, and 17). The text will introduce more of the possibilities that space imagery affords in monitoring and inventorying crops, grasslands, forests, wetlands, and other ecological niches. But now, let's examine ecological and other forms of damage brought on by geological events.
