2
a global biodiversity monitoring system (Jetz et al. 2016; Proença et al. 2017; The
National Academy of Sciences 2017). A central theme of this volume is that remote
sensing (RS) will play a key role in such a system.
1.2 Why a Focus on Plant Diversity?
Plants and other photosynthetic organisms form the basis of almost all primary productivity on Earth, and their diversity and function underpin virtually all other life
on this planet. Plants—collectively called vegetation—regulate the flow of critical
biogeochemical cycles, including those for water, carbon, and nitrogen. They affect
soil chemistry and other properties, which in turn affect the productivity and structure of ecosystems. Given the importance of plant diversity for providing the ecosystem services on which humans depend—including food production and the
regulating services that maintain clean air and freshwater supply (Millennium
Ecosystem Assessment 2005; IPBES 2018a)—it is critical that we monitor and
understand plant biodiversity from local to global scales, encompassing genetic
variation within and among species to the entire plant tree of life (Cavender-Bares
et al. 2017; Jetz et al. 2016; Turner 2014).
Of the 340,000 known seed plants on Earth and the 60,000 known tree species
(Beech et al. 2017), 1 out of every 5 seed plants and 1 out of every 6 tree species are
threatened (Kew Royal Botanic Gardens 2016). Vulnerability to threats ranging
from climate change to disease varies among species and lineages because of
evolved differences in physiology and spatial proximity to threats. Across all continents, the largest threat to terrestrial biodiversity is land use change due to farming
and forestry, while climate change, fragmentation, and disease loom as everincreasing threats (IPBES 2018a; b; c; d). Many plant species are at risk for extinction due to a combination of global change factors, including drought stress, exotic
species, pathogens, land use change, altered disturbance regimes, application of
chemicals, and overexploitation.
1.3 The Promise of Remote Sensing to Detect Plant Diversity
Different plants have evolved to synthesize different mixes of chemical compounds
arranged in contrasting anatomical forms to support survival and growth. In addition, the structures of plant canopies correspond to different growth strategies in
response to climate, environment, or disturbance. Differences among individual
plants, populations, and lineages result from contrasting evolutionary histories,
genetic backgrounds, and environmental conditions. Because these differences are
readily expressed in aboveground physiology, biochemistry, and structure, many of
these properties can be detected using spectral reflectance from leaves and plant
canopies (Fig. 1.1). Plant pigments absorb strongly electromagnetic radiation in the
J. Cavender-Bares et al.
a global biodiversity monitoring system (Jetz et al. 2016; Proença et al. 2017; The
National Academy of Sciences 2017). A central theme of this volume is that remote
sensing (RS) will play a key role in such a system.
1.2 Why a Focus on Plant Diversity?
Plants and other photosynthetic organisms form the basis of almost all primary productivity on Earth, and their diversity and function underpin virtually all other life
on this planet. Plants—collectively called vegetation—regulate the flow of critical
biogeochemical cycles, including those for water, carbon, and nitrogen. They affect
soil chemistry and other properties, which in turn affect the productivity and structure of ecosystems. Given the importance of plant diversity for providing the ecosystem services on which humans depend—including food production and the
regulating services that maintain clean air and freshwater supply (Millennium
Ecosystem Assessment 2005; IPBES 2018a)—it is critical that we monitor and
understand plant biodiversity from local to global scales, encompassing genetic
variation within and among species to the entire plant tree of life (Cavender-Bares
et al. 2017; Jetz et al. 2016; Turner 2014).
Of the 340,000 known seed plants on Earth and the 60,000 known tree species
(Beech et al. 2017), 1 out of every 5 seed plants and 1 out of every 6 tree species are
threatened (Kew Royal Botanic Gardens 2016). Vulnerability to threats ranging
from climate change to disease varies among species and lineages because of
evolved differences in physiology and spatial proximity to threats. Across all continents, the largest threat to terrestrial biodiversity is land use change due to farming
and forestry, while climate change, fragmentation, and disease loom as everincreasing threats (IPBES 2018a; b; c; d). Many plant species are at risk for extinction due to a combination of global change factors, including drought stress, exotic
species, pathogens, land use change, altered disturbance regimes, application of
chemicals, and overexploitation.
1.3 The Promise of Remote Sensing to Detect Plant Diversity
Different plants have evolved to synthesize different mixes of chemical compounds
arranged in contrasting anatomical forms to support survival and growth. In addition, the structures of plant canopies correspond to different growth strategies in
response to climate, environment, or disturbance. Differences among individual
plants, populations, and lineages result from contrasting evolutionary histories,
genetic backgrounds, and environmental conditions. Because these differences are
readily expressed in aboveground physiology, biochemistry, and structure, many of
these properties can be detected using spectral reflectance from leaves and plant
canopies (Fig. 1.1). Plant pigments absorb strongly electromagnetic radiation in the
J. Cavender-Bares et al.