Biodiversity is the abundance and variety of life found on Earth. It is important as it promotes ecosystem productivity, as well as the sustainability of life in general. A thriving, diverse ecosystem provides many benefits to humans. These ”ecosystem services” include nutrient storage and recycling, pollution filtration, water resource maintenance, and many others. Diverse ecosystems also provide many biological resources, such as food and medicines.
In a report from the United Nations Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (U.N. IPBES), researchers found an almost 20% decline in the average abundance of native species, as well as a sharp increase in the number of species now declared threatened. Thus monitoring biodiversity is critical. However, measuring biodiversity using field sampling can be costly and time-consuming and provides patchy information. Remote sensing data can fill in those gaps. When coupled with in-situ data, remote sensing data is critical for scientists and decision makers to make informed decisions. For more information on these statistics, read the U.N. IPBES Summary.
“Hyperspectral” remote sensing (also known as “imaging spectroscopy”) is a uniquely powerful technique for mapping and studying biodiversity. Like most optical remote sensing, it is based on the fact that different chemical compounds interact with light in different ways. For example, chlorophyll, the plant pigment responsible for light absorption in plants, strongly absorbs red and blue light but reflects green light. This allows us to estimate the chlorophyll content of a leaf by measuring how much red, green, and blue light is reflected. Other plant compounds have their own spectral signatures, and different plant species have different combinations of these compounds and therefore different spectral signatures. Numerous databases exist listing spectral signatures of plants and other natural surfaces, including the Ecological Spectral Information System (EcoSIS), the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) Spectral Library, and the Ecological Spectral Model Library (EcoSML).
All optical remote sensing of vegetation is based in some part on the ability to distinguish between spectral signatures of different plants—however, what distinguishes hyperspectral remote sensing is its large number of bands in narrow wavelength increments. For example, where Landsat 8 has just 3 bands in the visible range (red, green, and blue), a hyperspectral instrument might have 30 to over 300 (For more information on spectral resolution, read What is Remote Sensing?). Therefore, where Landsat and similar “multispectral” instruments can see only general land-cover classes, hyperspectral instruments can map individual species, making them an invaluable tool for studying habitat diversity.
Hyperspectral measures of leaf-surface attributes during different seasons can yield useful information about ecosystem functioning, change, and evolution. When analyzed together with other remotely derived indices (e.g., LAI or fraction absorbed photosynthetically active radiation (FPAR)) and assimilated into models that include soil-related parameters, hyperspectral data offer the potential to observe patterns of species diversity (from Turner, 2003).
NASA’s Airborne Visible/InfraRed Imaging Spectrometer (AVIRIS) and AVIRIS Next Generation (AVIRIS-NG) are unique optical sensors that deliver calibrated images of the spectral radiance received by the sensor in 224 contiguous spectral channels with wavelengths from around 400 to 2500 nanometers (nm). AVIRIS has been flown on four aircraft platforms. To see flight paths from 2006-2019, with accessible data, visit the AVIRIS Data Portal. AVIRIS-NG has been flown on three different platforms. To see flight paths from 2014-2019, with accessible data, visit the AVIRIS-NG Data Portal.
The Portable Remote Imaging Spectrometer (PRISM) comprises an imaging spectrometer covering the near-UV to near-IR range (350-1050 nm) and a separate spot radiometer covering two short wave infrared (SWIR) bands at 1240 and 1610 nm respectively. PRISM has been flown on several airborne platforms, specifically observing coastal zones. The PRISM Flight Locator Tool provides flight path information from 2014-2018.
The Hyperion instrument aboard NASA's Earth Observing-1 (EO-1) satellite detected 220 distinct wavelengths of light with a 30-meter resolution. The EO-1 satellite was launched on November 21, 2000 as part of a one-year technology validation/demonstration mission; however, the mission was extended due to interest from the remote sensing research and scientific communities. Data were collected through Data Acquisition Requests until 2017 when the satellite was decommissioned.
Research quality hyperspectral data products can be accessed directly via Earthdata Search. Datasets at Earthdata Search are site-specific.
- AVIRIS Hyperspectral Data from Earthdata Search
- PRISM Hyperspectral Data from Earthdata Search
- Hyperion Hyperspectral Data from Earthdata Search
The National Academies of Sciences, Engineering and Medicine (NASEM) chooses areas of priority for study called designated observables. The Surface Biology and Geology (SBG) Designated Observable, identified in the 2018 decadal survey "Thriving on Our Changing Planet: A Decadal Strategy for Earth Observation from Space,” has several observing priorities:
- Terrestrial vegetation physiology, functional traits, and health.
- Inland and coastal aquatic ecosystems physiology, functional traits, and health.
- Snow and ice accumulation, melting, and albedo.
- Active surface changes (eruptions, landslides, evolving landscapes, hazard risks).
- Effects of changing land use on surface energy, water, momentum, and C fluxes.
- Managing agriculture, natural habitats, water use/quality, and urban development.
SBG is currently in the initial phase of determining research and applications. For more information, view the SBG website.
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Published April 7, 2020