climax, seems to belong to the same biome. An
ecoregion, on the contrary, is never discontinuous (except on marine islands), though ecological communities that share similar characteristics
may exist in disjunct parts of the world.
Each ecoregion comprises both the climax
communities and all the successional stages
within its geographic area, and it thus includes
the freshwater communities. It does not, however, include the marine communities that may
lie adjacent to its shores. These communities
belong to the marine ecoregions, which are
discussed elsewhere in this volume.
Overviews of terrestrial biomes are common
in ecology and physical geography textbooks.
Detailed coverage of both terrestrial and marine
biomes may be found among the series of books
in the Greenwood Guides to Biomes of the World
(see Woodward 2009).
Other Ecoregional Classification
Systems
Global Mapping
The WWF developed an ecoregion classification
system to assess the status of the world’s wildlife
and conserve the most biologically valuable
ecoregions (Olson et al. 2001). The system is
well established within the organization’s structure and a world ecoregions map has recently
been published in collaboration with the National
Geographic Society. It was recently distributed
to all the US schools. Others have defined
ecoregions as areas of ecological potential
based on combinations of biophysical parameters
such as climate and topography. However, WWF
ecoregions emphasize the distribution of distinct
biotas, which often do not correspond to zones of
ecological potential for reasons such as historical
human activities, and chance events, or the complex differences regarding how living
communities respond to often subtle environmental conditions. Such mapping relies heavily
on expert judgment of species richness and endemism, unique higher taxa, unusual ecological or
evolutionary phenomena, and rarity of major
habitat types. The WWF-ecoregion framework
has been compared unfavorably to the Bailey
ecoregion system by Jepson and Whittaker
(2001).
Building on the work of the WWF, Abell et al.
(2008) developed a regionalization of freshwater
ecoregions of the world. They are large areas
encompassing one or more freshwater systems
with a distinct assemblage of natural freshwater
communities and species. They based their
ecoregion delineations on qualitative assessments
of similarity/dissimilarity using hydrological
regions or watershed boundaries and expert input.
The Nature Conservancy (TNC) developed a
global regionalization of coastal and shelf areas
called marine ecoregions (Spalding et al. 2007).
The approach relies on literature review and consultation with experts. They also developed a
spatial layer for the terrestrial ecoregions of the
world. This layer is based on WWF’s ecoregions
outside the United States and loosely based on
Bailey’s ecoregions within the United States.
This work parallels another ongoing effort to
derive a similar classification of the world’s
pelagic oceans (Spalding et al. 2012).
The Foreign Agricultural Organization (FAO)
(Simons 2001) of the United Nations developed a
global ecological zoning system based on
ecoregional concepts to collect information for
the Forest Resource Assessment 2000. The FAO
system follows Bailey (1989, 1995, 1998) in
using Ko ¨ppen’s climatic classification as a basis
for the delineation of zones. Mapping was carried
out using potential vegetation maps to define
boundaries of climatic zones at three hierarchical
levels. The system of global ecological zones has
recently been revised and updated (Foreign Agricultural Organization 2012).
The life zone system of Holdridge (1947) uses
annual precipitation and “biotemperature” (average days/year without temperatures <0 nor >30
C and potential evapotranspiration ratio, combining precipitation and biotemperature in an
index). This life zone system differentiates 38
life zone types. As average data are used, the
regions characterized by seasonal pattern are
not depicted in an appropriate way (Schwabe
Appendix D: Comparison of Ecoregion and Related Approaches
149
ecoregion, on the contrary, is never discontinuous (except on marine islands), though ecological communities that share similar characteristics
may exist in disjunct parts of the world.
Each ecoregion comprises both the climax
communities and all the successional stages
within its geographic area, and it thus includes
the freshwater communities. It does not, however, include the marine communities that may
lie adjacent to its shores. These communities
belong to the marine ecoregions, which are
discussed elsewhere in this volume.
Overviews of terrestrial biomes are common
in ecology and physical geography textbooks.
Detailed coverage of both terrestrial and marine
biomes may be found among the series of books
in the Greenwood Guides to Biomes of the World
(see Woodward 2009).
Other Ecoregional Classification
Systems
Global Mapping
The WWF developed an ecoregion classification
system to assess the status of the world’s wildlife
and conserve the most biologically valuable
ecoregions (Olson et al. 2001). The system is
well established within the organization’s structure and a world ecoregions map has recently
been published in collaboration with the National
Geographic Society. It was recently distributed
to all the US schools. Others have defined
ecoregions as areas of ecological potential
based on combinations of biophysical parameters
such as climate and topography. However, WWF
ecoregions emphasize the distribution of distinct
biotas, which often do not correspond to zones of
ecological potential for reasons such as historical
human activities, and chance events, or the complex differences regarding how living
communities respond to often subtle environmental conditions. Such mapping relies heavily
on expert judgment of species richness and endemism, unique higher taxa, unusual ecological or
evolutionary phenomena, and rarity of major
habitat types. The WWF-ecoregion framework
has been compared unfavorably to the Bailey
ecoregion system by Jepson and Whittaker
(2001).
Building on the work of the WWF, Abell et al.
(2008) developed a regionalization of freshwater
ecoregions of the world. They are large areas
encompassing one or more freshwater systems
with a distinct assemblage of natural freshwater
communities and species. They based their
ecoregion delineations on qualitative assessments
of similarity/dissimilarity using hydrological
regions or watershed boundaries and expert input.
The Nature Conservancy (TNC) developed a
global regionalization of coastal and shelf areas
called marine ecoregions (Spalding et al. 2007).
The approach relies on literature review and consultation with experts. They also developed a
spatial layer for the terrestrial ecoregions of the
world. This layer is based on WWF’s ecoregions
outside the United States and loosely based on
Bailey’s ecoregions within the United States.
This work parallels another ongoing effort to
derive a similar classification of the world’s
pelagic oceans (Spalding et al. 2012).
The Foreign Agricultural Organization (FAO)
(Simons 2001) of the United Nations developed a
global ecological zoning system based on
ecoregional concepts to collect information for
the Forest Resource Assessment 2000. The FAO
system follows Bailey (1989, 1995, 1998) in
using Ko ¨ppen’s climatic classification as a basis
for the delineation of zones. Mapping was carried
out using potential vegetation maps to define
boundaries of climatic zones at three hierarchical
levels. The system of global ecological zones has
recently been revised and updated (Foreign Agricultural Organization 2012).
The life zone system of Holdridge (1947) uses
annual precipitation and “biotemperature” (average days/year without temperatures <0 nor >30
C and potential evapotranspiration ratio, combining precipitation and biotemperature in an
index). This life zone system differentiates 38
life zone types. As average data are used, the
regions characterized by seasonal pattern are
not depicted in an appropriate way (Schwabe
Appendix D: Comparison of Ecoregion and Related Approaches
149