236
variables, including watershed size, soil water content (Moore et al. 1991), flow
paths, and surface water. In addition, two types of satellite data can be used to estimate soil moisture and groundwater, which in some systems are important drivers
of plant diversity because drought sensitivity may shape plant distributions (e.g.,
Engelbrecht et al. 2007). The ESA’s Soil Moisture and Ocean Salinity (SMOS;
launched 2009) and NASA’s Soil Moisture Active Passive observatory (SMAP;
launched 2015; Fig. 10.2) both use microwave radiometers to detect surface soil
moisture globally in areas with low topographic variation and low-vegetation cover.
The Gravity Recovery and Climate Experiment (GRACE; launched in 2002;
Fig. 10.2) is a pair of satellites that measure gravity anomalies around the world,
allowing researchers to estimate available groundwater reserves and their change
over time.
Water quality is a critical driver of aquatic biodiversity across taxa, from plants
to animals (Stendera et al. 2012). Watershed disturbance, sediment runoff, and
nutrient pollution are major aquatic biodiversity stressors, affecting phytoplankton
and aquatic and wetland vegetation abundance and diversity (Lacoul and Freedman
2006; Mouillot et al. 2013) and higher trophic levels (e.g., zooplankton, shrimps,
larval fish, and birds (Thackeray et al. 2010). Optical RS can be used to retrieve a
limited but important set of water quality variables, including particulate and dissolved organic and inorganic matter, chlorophyll-a, as well as other phytoplankton
pigments like the phycocyanins common in potentially harmful cyanobacteria
blooms. Surface or “skin” water temperature is measured from instruments with
thermal bands (Giardino et al. 2018; Alcântara et al. 2010). The major limitation in
RS of water quality is in sensor resolution. Sensors must have a fine enough pixel
size to resolve water bodies, with high enough radiometric sensitivity to detect
small changes in a dark target (10% or less of the total signal received by the sensor,
Muller-Karger et al. 2018; Hestir et al. 2015). While some water quality products
are publically distributed with limited spatial coverage [e.g., United Nations
Educational, Scientific and Cultural Organization (UNESCO) regions], free data
processors distributed by NASA (Sea-viewing Data Analysis System [SeaDAS])
and the ESA (Sentinel Application Platform) enable users to compute their own
water quality products.
10.3.4 Cryosphere
Earth’s fossil record illustrates how changes in glacial cover over time have governed the distribution of biodiversity (e.g., Veloz et al. 2012), and many aspects of
the globe’s biodiversity are influenced by snow, ice, and permafrost (reviewed by
Vincent et al. 2011). The frozen parts of the Earth system, the cryosphere, can be
detected with a number of different RS tools. The cryosphere can be divided into
several different components—seasonally snow-covered land, permafrost, glaciers
and ice sheets, lake ice, and sea ice. Because cloud cover is a frequent problem at
high latitudes, cryosphere RS often relies on longwave techniques that can pass
S. Record et al.
variables, including watershed size, soil water content (Moore et al. 1991), flow
paths, and surface water. In addition, two types of satellite data can be used to estimate soil moisture and groundwater, which in some systems are important drivers
of plant diversity because drought sensitivity may shape plant distributions (e.g.,
Engelbrecht et al. 2007). The ESA’s Soil Moisture and Ocean Salinity (SMOS;
launched 2009) and NASA’s Soil Moisture Active Passive observatory (SMAP;
launched 2015; Fig. 10.2) both use microwave radiometers to detect surface soil
moisture globally in areas with low topographic variation and low-vegetation cover.
The Gravity Recovery and Climate Experiment (GRACE; launched in 2002;
Fig. 10.2) is a pair of satellites that measure gravity anomalies around the world,
allowing researchers to estimate available groundwater reserves and their change
over time.
Water quality is a critical driver of aquatic biodiversity across taxa, from plants
to animals (Stendera et al. 2012). Watershed disturbance, sediment runoff, and
nutrient pollution are major aquatic biodiversity stressors, affecting phytoplankton
and aquatic and wetland vegetation abundance and diversity (Lacoul and Freedman
2006; Mouillot et al. 2013) and higher trophic levels (e.g., zooplankton, shrimps,
larval fish, and birds (Thackeray et al. 2010). Optical RS can be used to retrieve a
limited but important set of water quality variables, including particulate and dissolved organic and inorganic matter, chlorophyll-a, as well as other phytoplankton
pigments like the phycocyanins common in potentially harmful cyanobacteria
blooms. Surface or “skin” water temperature is measured from instruments with
thermal bands (Giardino et al. 2018; Alcântara et al. 2010). The major limitation in
RS of water quality is in sensor resolution. Sensors must have a fine enough pixel
size to resolve water bodies, with high enough radiometric sensitivity to detect
small changes in a dark target (10% or less of the total signal received by the sensor,
Muller-Karger et al. 2018; Hestir et al. 2015). While some water quality products
are publically distributed with limited spatial coverage [e.g., United Nations
Educational, Scientific and Cultural Organization (UNESCO) regions], free data
processors distributed by NASA (Sea-viewing Data Analysis System [SeaDAS])
and the ESA (Sentinel Application Platform) enable users to compute their own
water quality products.
10.3.4 Cryosphere
Earth’s fossil record illustrates how changes in glacial cover over time have governed the distribution of biodiversity (e.g., Veloz et al. 2012), and many aspects of
the globe’s biodiversity are influenced by snow, ice, and permafrost (reviewed by
Vincent et al. 2011). The frozen parts of the Earth system, the cryosphere, can be
detected with a number of different RS tools. The cryosphere can be divided into
several different components—seasonally snow-covered land, permafrost, glaciers
and ice sheets, lake ice, and sea ice. Because cloud cover is a frequent problem at
high latitudes, cryosphere RS often relies on longwave techniques that can pass
S. Record et al.