Early in the 20th century, as the scientific community grappled with the often confounding results of experiments that were ever so slowly laying the groundwork for quantum physics, the German physicist, Werner Heisenberg, made a profound comment about the nature of observation. “Natural science does not simply describe and explain nature,” Heisenberg said. “It is part of the interplay between nature and ourselves; it describes nature as exposed to our method of questioning.”
Heisenberg may have been remarking on a new study in which researchers used satellite remote sensing to analyze cloud cover around the world. What they found, or rather detected, was that variations in cloud cover helped them predict where different species live. The information could aid species conservation and management efforts.
Helmed by researchers with the University at Buffalo and Yale University, the study examines 15 years of images from NASA’s Terra and Aqua satellites. The data enabled the researchers to build a database of cloud cover for every square kilometer of Earth from 2000 to 2014.
CLOUD PATTERNS DEINFE ECOSYSTEM BOUNDARIES
Cloud patterns allow for a more precise prediction of species distribution from space instead of collecting data from ground observation, the most common approach used by conservationists. But the “terra firma” observation approach is limited because much of our planet's biodiversity is concentrated in hotspots like tropical mountains. In locales which pose access challenges, knowledge about the habitats and distributions of species remains uncertain to effectively guide management and conservation.
The study found that variations in cloud cover mark the boundaries of ecosystems, including tropical cloud forests that contain many species not found anywhere else in the world. Clouds directly affect local climates, causing differences in soil moisture and available sunlight that drive photosynthesis and ecosystem productivity.
"When we visualized the data, it was remarkable how clearly you could see many different biomes on Earth based on the frequency and timing of cloudy days over the past 15 years,"
says Adam Wilson, an ecologist at the University at Buffalo who led the study. "As you cross from one ecosystem into another, those transitions show up very clearly, and the exciting thing is that these data allow you to directly observe those patterns at 1-kilometer resolution."
REMOTE SENSING INSTRUMENTS
According to BCC Research analyst Jim Wilson (no relation to Adam Wilson), the remote sensing industry creates products and services that extend, enhance and organize the way we see the world. The industry’s global network of precisely calibrated instruments mounted on airborne, aquatic, space-based and terrestrial platforms capture infinitesimally small amounts of energy reflected from targets at distances from feet to miles away, and transform it into products and services that provide information for applications from predicting harvests to protecting wildlife and preventing pandemics.
Sensors are the tools we use to question nature, as humans and as scientists. Our natural human senses question nature through a narrow window defined by the limitation of the central nervous system.
“Artificial sensing instruments developed by the scientific community fling open that window, allowing us to observe a broader and richer view of the universe than human physiology permits,” Wilson says. “Looking outward, the Hubble Space Telescope captures light from the most distant reaches of the universe, more than 13 billion light years from earth. Looking inward, scanning tunneling microscopes reveal the very shape of the atoms that form every object that surrounds us. Devices that amplify acoustical energy reveal sounds at frequencies far below and above human hearing.”
WHAT ARE PASSIVE REMOTE SENSING INSTRUMENTS?
Broadly speaking, there are two types of sensors: direct sensors that respond to the presence of specific types of molecules; and remote sensors that respond to the presence of specific types of energy.
Remote sensing instruments broadly divide themselves into two types: passive and active. Passive instruments detect ambient energy levels, typically electromagnetic energy in the visible and near infrared range, and to a lesser degree mechanical motion associated with sound and seismic activity. Active remote sensing requires a dedicated energy source, in the form of a radar signal, coherent beam of light from a laser or acoustic ping of a sonar device.
Passive remote sensing instruments respond to ambient energy. Electromagnetic energy that originates from the sun and which we perceive as visible light range is the most ubiquitous ambient energy source. Lesser known forms of ambient energy include seismic activity, used to detect earthquakes and infrasound used to underground explosions and slow movements of geologic materials. Generally speaking, passive instruments are distinguished by the range of frequency of the electromagnetic energy or mechanical
motion they detect.
Wilson says that because remote sensing instruments used on airborne and space-based platforms are exclusively passive instruments, data collection is limited to reflected radiation across the visible light portion of the electromagnetic spectrum and several bands within the invisible region. The source of illumination for the observation is obviously the sun, he notes.
REMOTE SENSING OF CLOUD COVER UNCOVERS BIODIVERSITY
Cloud cover also helped the researchers better predict where specific species live. By taking cloud patterns into account, the team was able to determine the size and location of habitats for the montane woodcreeper (a South American bird) and king protea (a South African shrub) in unprecedented detail and accuracy.
That finding is particularly exciting because the technique could be used to research the habitats of threatened plants and animals, says co-author Walter Jetz, associate professor of ecology and evolutionary biology at Yale University.
"Understanding the spatial patterns of biodiversity is critical if we want to make informed decisions about how to protect species and manage biodiversity and its many functions into the future," Jetz
says.
The study demonstrates how remote sensing can be a powerful tool in those efforts, Wilson says. "That's one of the really exciting developments in the field today. We now have decades of satellite observations that we can pull together to characterize the global environment.” He notes that Aqua and Aura have been collecting two images per day everywhere on Earth for well over a decade. "It is exciting to now be able to tap into this large stack of detailed data to support global biodiversity and ecosystem monitoring and conservation.
BCC Research analyst Jim Wilson anticipates the global market for remote sensing products to reach nearly $8.9 billion in 2016 and $13.8 billion by 2021, reflecting a five-year compound annual growth rate (CAGR) of 9.3%.
