|Who Are NASA's Earth Explorers?
The elementary school student questioning if El Niño occurs anywhere besides the Pacific Ocean. The researcher investigating connections between Arctic ozone depletion and global climate change. The citizen scientist interested in how changing land cover and use affects animal migration patterns. And the businessperson projecting future needs for harvest, delivery and storage of crops. All of these people are Earth Explorers -- they are all connected by their curiosity about Earth system processes. This series will introduce you to NASA Earth Explorers, young and old, with a variety of backgrounds and interests.
Adam Johnson's approximately 24-hour, 5,000-mile trip from Maryland to the western coast of Ghana earlier this year was the longest he had ever taken. But it was nothing compared to the months-long reverse journey -- from the shores of West Africa to the Americas -- that millions of enslaved Africans were forced to experience centuries earlier.
Image to left: Standing in a Ghanaian palm plantation, Johnson calculates his exact location with a global positioning system (GPS) receiver. Credit: Coppin State
From the 1400s to 1800s, approximately 20 million people were kidnapped from interior areas of Africa and made to walk hundreds of miles to the coast. Those who survived the grueling hike -- only about half -- then boarded ships that would take as long as four months to sail the Atlantic Ocean and deposit them as slaves in North America, South America or the Caribbean.
Unlike his oppressed ancestors, Johnson, an undergraduate at Baltimore's Coppin State University, traveled in January to Africa's Cape Coast out of his own volition. Johnson and Coppin State geography professor Douglas Reardon were there to get a firsthand look at an area they had been studying from satellite imagery as part of the school's "Middle Passage Project," which has students combining remote sensing and other environmental data with historical records to gain new insights on the transatlantic slave trade.
The voyage of slaves across the Atlantic is commonly referred to as the "Middle Passage" because it constituted the middle segment of a three-part trade route. In the first leg, ships would travel from Europe to Africa with rum, cloth, guns and other goods to be exchanged for slaves. Hundreds of slaves would then be packed like sardines onto a single ship before it set sail for the Americas -- the second leg -- where the surviving slaves (10 to 20 percent died at sea) would be traded for commodities such as sugar, tobacco and cotton. The return trip to Europe was the third and final leg.
Image to right: Douglas Reardon is Adam Johnson's geography teacher. Credit: Coppin State
The Europeans built dozens of fortresses along the West African coast to house slaves while they waited, sometimes a full year, for their ships to arrive. Johnson and Reardon have been examining how the land has changed over the years in the area of these fortresses, many of which still exist today as tourist attractions. The project ties geoscience together with a theme that is especially relevant to students at Coppin State, a historically black university.
"We were answering a scientific question of interest to NASA -- namely, how has the land changed and what's driving it -- in a portion of the world where many of my students have a real sincere interest," Reardon said.
According to Johnson and Reardon, images captured by NASA's Landsat satellite indicate that logging and agricultural activities have destroyed much of the rainforest along the West African coast over the last 25 years, with the exception of areas such as Kakum National Park, a rainforest preserve established to promote tourism and maintain a balance between commercial and environmental interests.
The view from outer space isn't always picture perfect, however. Surveying the land in person allowed Johnson and Reardon to more clearly identify the kinds of agriculture that had overrun previously forested areas. With the help of a global positioning system receiver, the researchers were able to note the exact locations of different types of land cover.
Image to left: This map shows where Ghana is in relation to the rest of the world. Credit: Wikipedia
"Even though we had the satellite imagery... we couldn't always distinguish between different agricultural areas," Johnson said. "Actually being down there on the ground we were able to distinguish between them."
Reardon notes that, in addition to the scientific advantage gained by seeing the land with their own eyes, there is a cultural significance to visiting a region that played host to an important chapter in African-American history.
"For Adam... I think it was an incredible experience," Reardon said. "Here's an opportunity to get your boots on the ground in a part of the world where as an African-American you're just fascinated with."
Back home, Johnson and Reardon are now using a geographic information system, "GIS," to overlay the Landsat imagery with the data they collected in Ghana. Reardon plans to publish their findings in a scientific journal, and to incorporate the results into educational lessons for his undergraduate geography courses.
In a second component of the Middle Passage Project, Johnson is assisting Reardon in an effort to determine whether wind patterns and ocean currents can be correlated with death rates on slave ships. Both components were funded by NASA's Minority University-Space Interdisciplinary Project, an initiative to train the next generation of minority scientists and engineers.
It looks like Johnson will continue his work with GIS and remote sensing even after graduating from Coppin State. Johnson is taking part in a National Geospatial-Intelligence Agency program that will lead to full-time employment with the agency, which provides geospatial intelligence in support of U.S. national security.
Johnson says he is looking forward to a career in solving problems with GIS and other tools.
"The Earth is forever changing," he said. "We need people to constantly monitor those changes."
See previous Earth Explorers articles:
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Kids Science News Network™: How do satellites help us study Earth from space?
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Minority University-Space Interdisciplinary Project (MU-SPIN)
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Dan Stillman, Institute for Global Environmental Strategies