Cross-references
Environmental Gradients
Estuarine Habitat Restoration
Habitat Loss
Shannon-Weaver Diversity Index
HABITAT LOSS
Laura Airoldi
1 and Michael W. Beck
2
1
Dipartimento di Scienze Biologiche, Geologiche e
Ambientali, University of Bologna, Ravenna, Italy
2
The Nature Conservancy, Center for Ocean Health,
University of California, Santa Cruz, CA, USA
Synonyms
Habitat clearing; Habitat conversion; Habitat destruction;
Habitat reduction
Definition
Airoldi and Beck (2007) have defined habitat loss as
a measurable reduction in the abundance and distribution
of natural habitats. Habitat loss is a term that is now in
widespread use because of the ongoing impacts on natural
systems associated with human population growth and the
increasing need for development space and natural
resources (Millennium Ecosystem Assessment, 2005).
At the same time, the term “habitat loss” is often defined
in inconsistent ways. Most often “habitat” refers to the
predominant features that create structural complexity in
the environment, such as plants (e.g., pine forests, sea
grass meadows) or animals (e.g., coral reefs), and “loss”
indicates a focus on a measurable reduction in habitat
cover (i.e., areal extent). Loss clearly occurs when natural
habitats, such as forests, are cut down and slated for
construction of buildings and roads or when salt marshes
are filled with sediments and blocked from the sea to form
agricultural fields. Sometimes the loss of one habitat can
mean the gain in another habitat such as when seagrasses
die from disease outbreaks and sand or mudflats remain.
Even in these cases of transition, the common transition
is from a more to a less structurally complex habitat. It is
very rare for an area to transition from a less to a more
structurally complex habitat unless there is active habitat
restoration. In the oceans, this widespread phenomenon
has been referred to as the flattening of the marine bottom.
Habitat degradation (alteration or change) often is
a precursor to the loss of natural habitats. However, degradation is difficult to measure because it represents
a change in condition, not a change in distribution (i.e.,
habitat loss). Habitat fragmentation falls between loss
and degradation (Bender et al., 1998). Fragmentation
occurs when previously continuous habitats become
patchy or less dense (e.g., loss of patches of trees within
a larger forest). The distinction between loss and fragmentation is generally one associated with monitoring
resolution because many large-scale surveys and spatial
imagery do not capture increases or decreases in
patchiness.
The term habitat loss is most commonly used to refer to
the destruction of natural habitats as a direct or indirect
consequence of many human activities, including urban
development, organic and inorganic pollution, and
overexploitation of resources. Habitat loss, however, can also
occur as a result of natural events such as floods, droughts,
volcanic eruptions, earthquakes, and climate fluctuations.
Habitat loss is ranked among the leading causes of species extinction both in terrestrial and marine systems
(Pimm and Raven, 2000; Airoldi et al., 2008). Indeed,
habitat loss results in the immediate extirpation of local
populations of resident species and the loss of the ecosystem functions and services that these populations provided
(Millennium Ecosystem Assessment, 2005).
Bibliography
Airoldi, L., and Beck, M. W., 2007. Loss, status and trends for
coastal marine habitats of Europe. Oceanography and Marine
Biology: An Annual Review, 45, 345–405.
Airoldi, L., Balata, D., and Beck, M. W., 2008. The Gray Zone:
relationships between habitat loss and marine diversity and their
applications in conservation. Journal of Experimental Marine
Biology and Ecology, 366, 8–15.
Bender, D. J., Contreras, T. A., Fahrig, L., 1998 Habitat loss and
population decline: A meta-analysis of the patch size effect.
Ecology, 79, 517–533.
Millennium Ecosystem Assessment, 2005. Ecosystems and Human
Well-Being: Synthesis. Washington, DC: Island Press.
Pimm, S. L., and Raven, P., 2000. Biodiversity - extinction by
numbers. Nature, 403, 843–845.
Cross-references
Estuarine Habitat Restoration
Habitat Complexity
HALOCLINE
Evgeniy Yakushev
Section of Oceanography and Remote Sensing,
Norwegian Institute for Water Research (NIVA), Oslo,
Norway
Definition
A halocline is a vertical zone in the water column in which
salinity changes rapidly with depth (Halocline, 2013).
Description
Haloclines in the ocean are either seasonal or permanent.
In coastal inlets, lagoons, fjords, and poorly mixed estuaries, haloclines form where freshwater overlies seawater.
A vertical salinity gradient in haloclines can reach
46 PSU m
À1 (50-cm layer of Fjord Hunnbunn, Norway;
Yakushev et al., 2013).
HALOCLINE
349
Environmental Gradients
Estuarine Habitat Restoration
Habitat Loss
Shannon-Weaver Diversity Index
HABITAT LOSS
Laura Airoldi
1 and Michael W. Beck
2
1
Dipartimento di Scienze Biologiche, Geologiche e
Ambientali, University of Bologna, Ravenna, Italy
2
The Nature Conservancy, Center for Ocean Health,
University of California, Santa Cruz, CA, USA
Synonyms
Habitat clearing; Habitat conversion; Habitat destruction;
Habitat reduction
Definition
Airoldi and Beck (2007) have defined habitat loss as
a measurable reduction in the abundance and distribution
of natural habitats. Habitat loss is a term that is now in
widespread use because of the ongoing impacts on natural
systems associated with human population growth and the
increasing need for development space and natural
resources (Millennium Ecosystem Assessment, 2005).
At the same time, the term “habitat loss” is often defined
in inconsistent ways. Most often “habitat” refers to the
predominant features that create structural complexity in
the environment, such as plants (e.g., pine forests, sea
grass meadows) or animals (e.g., coral reefs), and “loss”
indicates a focus on a measurable reduction in habitat
cover (i.e., areal extent). Loss clearly occurs when natural
habitats, such as forests, are cut down and slated for
construction of buildings and roads or when salt marshes
are filled with sediments and blocked from the sea to form
agricultural fields. Sometimes the loss of one habitat can
mean the gain in another habitat such as when seagrasses
die from disease outbreaks and sand or mudflats remain.
Even in these cases of transition, the common transition
is from a more to a less structurally complex habitat. It is
very rare for an area to transition from a less to a more
structurally complex habitat unless there is active habitat
restoration. In the oceans, this widespread phenomenon
has been referred to as the flattening of the marine bottom.
Habitat degradation (alteration or change) often is
a precursor to the loss of natural habitats. However, degradation is difficult to measure because it represents
a change in condition, not a change in distribution (i.e.,
habitat loss). Habitat fragmentation falls between loss
and degradation (Bender et al., 1998). Fragmentation
occurs when previously continuous habitats become
patchy or less dense (e.g., loss of patches of trees within
a larger forest). The distinction between loss and fragmentation is generally one associated with monitoring
resolution because many large-scale surveys and spatial
imagery do not capture increases or decreases in
patchiness.
The term habitat loss is most commonly used to refer to
the destruction of natural habitats as a direct or indirect
consequence of many human activities, including urban
development, organic and inorganic pollution, and
overexploitation of resources. Habitat loss, however, can also
occur as a result of natural events such as floods, droughts,
volcanic eruptions, earthquakes, and climate fluctuations.
Habitat loss is ranked among the leading causes of species extinction both in terrestrial and marine systems
(Pimm and Raven, 2000; Airoldi et al., 2008). Indeed,
habitat loss results in the immediate extirpation of local
populations of resident species and the loss of the ecosystem functions and services that these populations provided
(Millennium Ecosystem Assessment, 2005).
Bibliography
Airoldi, L., and Beck, M. W., 2007. Loss, status and trends for
coastal marine habitats of Europe. Oceanography and Marine
Biology: An Annual Review, 45, 345–405.
Airoldi, L., Balata, D., and Beck, M. W., 2008. The Gray Zone:
relationships between habitat loss and marine diversity and their
applications in conservation. Journal of Experimental Marine
Biology and Ecology, 366, 8–15.
Bender, D. J., Contreras, T. A., Fahrig, L., 1998 Habitat loss and
population decline: A meta-analysis of the patch size effect.
Ecology, 79, 517–533.
Millennium Ecosystem Assessment, 2005. Ecosystems and Human
Well-Being: Synthesis. Washington, DC: Island Press.
Pimm, S. L., and Raven, P., 2000. Biodiversity - extinction by
numbers. Nature, 403, 843–845.
Cross-references
Estuarine Habitat Restoration
Habitat Complexity
HALOCLINE
Evgeniy Yakushev
Section of Oceanography and Remote Sensing,
Norwegian Institute for Water Research (NIVA), Oslo,
Norway
Definition
A halocline is a vertical zone in the water column in which
salinity changes rapidly with depth (Halocline, 2013).
Description
Haloclines in the ocean are either seasonal or permanent.
In coastal inlets, lagoons, fjords, and poorly mixed estuaries, haloclines form where freshwater overlies seawater.
A vertical salinity gradient in haloclines can reach
46 PSU m
À1 (50-cm layer of Fjord Hunnbunn, Norway;
Yakushev et al., 2013).
HALOCLINE
349