Landsat over Lolo

Nature, well-educated offspring of the Age of Enlightenment such as Thomas Jefferson and his friends in Philadelphia whom Lewis sought as mentors, believed in one overriding purpose in human existence: to study the world about and beyond them, to learn to name and identify its elements, and to synthesize their knowledge into a holistic understanding of the Earth and its celestial context. They were devoted to the study of all of the hoops that make up the whole circle of the universe.

As naturalists, Lewis and Clark did their work subjectively, with specimens they could approach and often hold in their hands to study at the level defined by those “faculties of the Soul,” the five senses.^[2]At Camp Dubois, evidently in January 1804, William Clark copied a paragraph on “Senses” from the encyclopedia Lewis had brought along, Owen’s Dictionary of Arts and Sciences, into … Continue reading Lewis recorded certain particularities of the plants, animals,and people he walked among. He counted, measured, weighed, watched, listened, smelled, and tasted. He synthesized, compared, and made rudimentary verbal maps of habitats, climatic zones, ecosystems, and patterns of human occupancy and use. He could begin to place disparate small details into larger contexts, and speculate on the seasonal and spatial maps of bears and bison, birds, fish, and trees. Every little answer resonates with its inherent query.

By the time he arrived at the Pacific Ocean he could compare grouse he saw there with those he remembered on the East Coast, as well as those on the high plains and in the Rockies along K’useyneiskit.^[3]K’useyneiskit is a Nez Perce name for the road they followed annually across the Rockies to the buffalo country on the upper Missouri River (see Road to the Buffalo). It has also been known as … Continue reading He could distinguish between meadowlarks from the fields of Virginia and those of the high plains. He could recognize and record the ecotones of different species of cottonwood trees. He was not always right, but he tried.

He made a significant beginning toward the mapping of ecosystems, and began to understand the juxtaposition and the interlocking of ecosystems and habitats. Knowing his own limitations, he nonetheless made a stab at descriptions with scientific precision, but refrained from assuming the prerogatives of an experienced laboratory scientist; he never established type specimens. He knew there was more to be done, and knew there were trained scientists who were poised to carry understanding to its next level, to place all the details they could observe, including his, into the larger and ostensibly more objective framework of Carl Linnæus’s systematic taxonomy and its contemporary variants.

Indeed, the systematics that Linnæus established continued to be refined and revised throughout the 19th century and well into the 20th. In the 1930s a new level of technology provided new ways of studying the land—aerial photography.^[4]Actually, aerial photography began in the 1860s both in the U.S. and in Italy, using hot-air balloons as platforms from which to shoot photos for purposes of military reconnaissance, if not just for … Continue reading

The work that Meriwether Lewis, his mentors, and his contemporaries began is not yet done. The quest for that ultimate understanding still goes on, driven now by awareness of the common molecular elements of all life. Botanists and biologists continue to use the basic tools Lewis and his contemporaries employed, but they also revisit the same species, and even the same specimens, equipped with microanalytical information systems to study them at the level of genetics and DNA. Equally revolutionary is the new means of expanding the worldwide scope at new levels of analysis—the orbiting space platform represented by the Landsat program. The discovery continues.

Viewed from approximately 460 miles above the Earth in an image that encompasses approximately 17,000 square miles, the realm where we live looks like a chaos of textures and colors. At right is the Bitterroot River valley, defined on the west by the main Bitterroot Range already dusted with the snows of autumn, and on the east by the Sapphire Mountains.

Notice the checkerboard pattern of light and dark green dots—actually 1-mile squares—that are visible just to the right of center (there are more at extreme bottom right).

Figures 3–5 are excerpts from full satellite “scenes” acquired by the Thematic Mapper (TM) sensor on board the Landsat 5 and Landsat 7 satellites.^[5]Landsat 6, launched in October 1993, failed to reach orbit. Those satellites are the most recent in chronological sequence that began with the launching of Landsat 1 in 1972. The project, which began under the National Aeronautics and Space Administration and is now administered by the United States Geological Survey, was conceived and implimented for the express purposes of monitoring the health of the Earth and facilitating a better understanding of the complex interactions that drive global change. Satellite images such as these have been used in a wide variety of ways—measuring the ebb and flow of glaciers, tracking population changes in and around metropolitan areas, measuring droughts and floods, the effects of global warming, and many other applications in geology, agriculture, forestry, education, etc.

Landsats 5 and 7 currently (2005) are in geosynchronous^[6]Geosynchronous means that each satellite remains stationary relative to the Earth and the sun throughout the earth’s daily orbit, while the earth revolves and tilts beneath it. Therefore the … Continue reading orbit approximately 435 miles above the Earth. Even at that distance, their sensors can “see” features on the planet as small as 30 meters (98.4 feet) square. Each 30-meter square is represented by one pixel (one seventy-seconds of an inch) of a digital image. The space vehicles, called satellite platforms, are designed to cover the entire Earth in a synchronized path every sixteen days. Landsat 5 is coordinated with Landsat 7 so as to enable the sensors on board to revisit the same area once every eight days, allowing scientists to quantify changes that take place between image dates, and to develop appropriate land management strategies.

The two examples shown to the right are of an identical area, centering on Lolo Pass and Packer Meadows, taken eleven years apart. The colors are not those we would normally associate with the features depicted. Instead, they represent what is known as a false-color composite, in which colors are defined in terms of the bands^[7]Bands are wavelengths of radiation. Landsat 5 is capable of sensing seven different wavelengths; Landsat 7 records eight. The Thematic Mapper is the satellite’s sensor that reads bands of solar … Continue reading of data are displayed—in this instance band 3, which is visible red; band 4, near-infrared; and band 5, mid-infrared. The false-color convention is superior to natural colors for purposes of scientific analysis because it is not subject to the atmospheric interferences that we take for granted at eye level. For example, we all know that trees are green, yet we’re also thrilled by those “purple mountains’ majesty,” and we’ve seen hillsides of trees that look almost black from a certain distance. But by sensing ground cover digitally as a complex set of reflections of electromagnetic waves, and then converting them into arbitrarily assigned colors in the visual spectrum, there can be no doubt as to which waves come from trees.

In the above image, land devoid of any vegetation appears as white, gray, or shades of blue due to the high reflectivity of those surfaces, whereas water, which absorbs almost all radiation, is black. Healthy living vegetation, however, is represented by shades of orange and red. The deeper the red, the greener and more dense the vegetation.

Thus the intact coniferous forests of the Lolo Pass area appear dark red, while the sparse vegetation in the clear-cuts appears as light orange. Those differences in color are really differences in reflectance values. In other words, each pixel in the image, representing 30 square meters, has a number associated with the amount of reflectance in each of the eight bands of radiation sensed by the ETM+. Those numeric values allow scientists not only to study the images by looking at them, but also to perform complex statistical calculations that may reveal information that is invisible to the eye.

The simple comparisons shown in these three images are merely the surface of this new realm of scientific investigation. Special software programs are capable of identifying the dominant types of vegetation that existed at the time the first image was captured in 1989 and what remains in 2000, or has been added or removed in the intervening eleven years. Observations made this way, in this place, enable scientists and land managers to assess the health of the ground cover in and around the Lolo Pass area, and to make decisions that will help to ensure the preservation of a site that is important to our historical and ecological heritage.

The on-the-ground, hands-on modes of study and analysis that scientists used at the opening of the 19th century are still necessary. However, we may suppose that Lewis and Clark would be fascinated and inspired by this giant, space-age leap in our ability to understand the world around us today.

Reviewed by Marjorie Lubinski and Robert Bergantino.