Threatened Habitats
Books, articles and sites on Habitat loss
What is Habitat? Habitat, is the natural environment in which an
organism lives and evolved in or has adapted to, and the physical
environment that surrounds (influences and is utilized by) a species
population. While some species range widely through their
environment, many have very localized habitats. It is often
convenient for those who would exploit the Environment to limit their
consideration of a species' or organism's habitat to such a
geographically restricted locale. However this ignores the wider
influences and dependencies between a habitat and the environment
around it, whose existence both influences and buffers it.
For example, a developer who
wishes to build a Wind Generating Station
in a forested wetland area where Braun's Holly Fern or Oval-leaved
Bilberry is found, will be required to protect the immediate
surroundings of these plants as they are considered rare and hence a
protected species. However, will even a 120 meter setback from
development protect these plants when the surrounding forest and
watershed is severely disrupted and the drying effect of Industrial
Wind Turbines coupled with increased erosion and increased light
penetration due to deforestation are significant factors changing the
micro climate in the larger surroundings?
The Developer, and the Consultants he pays, will naturally assert that
none of these impacts are significant and that there is no danger to
the plants. They will even sometimes emplace monitoring and
mitigation protocols at the request of the MOE or the MNR.
However the very fact that one has to consider a monitoring protocol
implies that there is no certainty at all in their assertions.
The adoption of an a priori mitigation strategy is planning for
failure. While seemingly sensible and responsible these measures
are actually an exercise in avoidance of liability. They can
point to these measure and claim that they have done all that a
reasonable person (a legal test of liability) could be expected to do.
In that they are only plants or animals or a small ecology, and given
the MOE's and MNR's mandates to exploit our natural heritage as
efficiently as possible, the developer will be excused as 'it was
unforseeable' and allowed to continue with business as usual. We
see this exact scenario playing out at Wolfe Island where thousands of
birds & bats have been killed by the IWT there. The MNR is
'surprised' and 'concerned' and have accepted the developer's
recommendation to 'mitigate' the problem - by studying it further...
It is a carefully orchestrated performance with lots of smoke and
mirrors, but it carefully ignores considering one thing: a reasonable
person would have foreseen that erecting 132 Industrial Wind Turbines
across a major North American migratory bird route would kill thousands
of birds. Wind Generating Stations have been killing birds for over 30 years, so I wonder at their surprise.
The same 'planning' and 'stringent environmental protection' is being
demonstrated by the MNR and MOE as they approve the Ostrander Point and
White Pines Wind Generating Stations which will also be on major bird
migratory routes. No doubt they will be 'surprised' and
'concerned' when even more raptors, songbirds and bats are killed at
these projects, and tell us, with a straight face, that no one could
have forseen the problem.
This calculation of liability and tacit collusion with Government
bureaucracies is not new, car companies have done it with gas tanks
that explode, vehicles that accelerate rapidly on their own
etc... If even 1/10th of the deaths occuring at these IWT were
human, the willful blindness to the obvious would be swept away in a
tide of indignation and recrimination. However these are only
animals and human societies have always exploited and killed those
weaker than themselves, especially when it is safe to do so.
The MOE and MNR make grandiose
statements about environmental protection, and are quite happy to
prosecute private individuals and farmers, but seem less anxious to
enforce environmental protection laws and treaties when it would
inconvenience big business, especially with the Ontario Government
backing Wind Power at all costs.
Government bureaucracies in Canada have a very poor record when it
comes to managing ennvironmental protection in the face of Government
pressure to facilitate commercial exploitation of a resource. The
DFO and the Cod fishery is a perfect example. The same scenario
is playing out on the West coast with the Salmon. The MNR's claim
to protect bio-diversity is problematic. The MNR doesn't appear
to recognize Significant Wildlife Habitat and bio-diversity until it
has been reduced to tiny checkerboard enclaves surrounded by
development. Here on the Shore of Lake Superior, despite a
long history of logging and mining the environment is still
largely intact. Yet now the MNR encourages the checkerboarding of
this landscape with Wind Generating Stations.
Bio-diversity is impossible to maintain in the face of habitat
fragementation. Habitat fragmentation has been shown to lead to
the extirpation or extinction of 40% or more of the species that lived
in the intact environment. This is not cutting edge science, this
is well established and well known to biologists and other natural
scientists.
So why are we disturbed about a few dead birds, bats or plants?
Apart from the fact that the creatures we share this planet with have
as much right to exist as we do, it is entirely possible that the
ecology which supports our existence may well lose its human carrying
capacity as a result of losing too many species, not all of which are
charismatic mega-fauna.
Even so, the loss of so many species, of places that will henceforth
only exist in Group of Seven paintings will surely diminish us.
Consequences of Habitat Fragmentation explained through a simple experiment
Ackerly - The geography of climate change/ implications for conservation biogeography 23 MAR 2010 (Word Document)
Ackerly Climate Change Data Supporting Document (PDF)
Effects of Habitat Fragmentation on Birds and Mammals in Landscapes with Different Proportions of Suitable Habitat: A Review
Henrik Andrén
Oikos
Vol. 71, No. 3 (Dec., 1994), pp. 355-366
(article consists of 12 pages)
Published by: Blackwell Publishing on behalf of Nordic Society Oikos
Abstract
Habitat fragmentation implies a
loss of habitat, reduced patch size and an increasing distance between
patches, but also an increase of new habitat. Simulations of patterns
and geometry of landscapes with decreasing proportion of the suitable
habitat give rise to the prediction that the effect of habitat
fragmentation on e.g. population size of a species would be primarily
through habitat loss in landscape with a high proportion of suitable
habitat. However, as the proportion of suitable habitat decreases in
the landscape, area and isolation effects start influencing the
population size of the species. Hence, the relative importance of pure
habitat loss, patch size and isolation are expected to differ at
different degrees of habitat fragmentation. This conclusion was
supported by a review of studies on birds and mammals in habitat
patches in landscapes with different proportions of suitable habitat:
the random sample hypothesis was a good predictor of the effects of
habitat fragmentation in landscapes with more than 30% of suitable
habitat. In these landscapes, habitat fragmentation is primarily
habitat loss. However, in landscapes with highly fragmented habitat,
patch size and isolation will complement the effect of habitat loss and
the loss of species or decline in population size will be greater than
expected from habitat loss alone. Habitat patches are parts of the
landscape mosaic and the presence of a species in a patch may be a
function not only of patch size and isolation, but also of the
neighbouring habitat. Habitat generalists may survive in very small
patches because they can also utilize resources in the surroundings.
Furthermore, the total species diversity across habitats in a given
landscape may increase when new patches of habitat are created within
the continuous habitat, since new species may be found in these new
habitats, even if they are human-made.
EFFECTS OF HABITAT FRAGMENTATION ON BIODIVERSITY
Annual Review of Ecology, Evolution, and Systematics
Vol. 34: 487-515 (Volume publication date November 2003)
First published online as a Review in Advance on August 14, 2003
DOI: 10.1146/annurev.ecolsys.34.011802.132419
Lenore Fahrig
Ottawa-Carleton Institute of Biology, Carleton University, Ottawa, Ontario, Canada K1S 5B6
Abstract
The literature on effects of
habitat fragmentation on biodiversity is huge. It is also very diverse,
with different authors measuring fragmentation in different ways and,
as a consequence, drawing different conclusions regarding both the
magnitude and direction of its effects. Habitat fragmentation is
usually defined as a landscape-scale process involving both habitat
loss and the breaking apart of habitat. Results of empirical studies of
habitat fragmentation are often difficult to interpret because (a) many
researchers measure fragmentation at the patch scale, not the landscape
scale and (b) most researchers measure fragmentation in ways that do
not distinguish between habitat loss and habitat fragmentation per se,
i.e., the breaking apart of habitat after controlling for habitat loss.
Empirical studies to date suggest that habitat loss has large,
consistently negative effects on biodiversity. Habitat fragmentation
per se has much weaker effects on biodiversity that are at least as
likely to be positive as negative. Therefore, to correctly interpret
the influence of habitat fragmentation on biodiversity, the effects of
these two components of fragmentation must be measured independently.
More studies of the independent effects of habitat loss and
fragmentation per se are needed to determine the factors that lead to
positive versus negative effects of fragmentation per se. I suggest
that the term "fragmentation" should be reserved for the breaking apart
of habitat, independent of habitat loss.
Habitat Fragmentation Effects on Birds in Grasslands and Wetlands: A Critique of Our Knowledge (full article)
Douglas H. Johnson
Abstract
Habitat fragmentation exacerbates
the problem of habitat loss for grassland and wetland birds. Remaining
patches of grasslands and wetlands may be too small, too isolated, and
too influenced by edge effects to maintain viable populations of some
breeding birds. Knowledge of the effects of fragmentation on bird
populations is critically important for decisions about reserve design,
grassland and wetland management, and implementation of cropland
set-aside programs that benefit wildlife. In my review of research that
has been conducted on habitat fragmentation, I found at least five
common problems in the methodology used. The results of many studies
are compromised by these problems: passive sampling (sampling larger
areas in larger patches), confounding effects of habitat heterogeneity,
consequences of inappropriate pooling of data from different species,
artifacts associated with artificial nest data, and definition of
actual habitat patches. As expected, some large-bodied birds with large
territorial requirements, such as the northern harrier (Circus
cyaneus), appear area sensitive. In addition, some small species of
grassland birds favor patches of habitat far in excess of their
territory size, including the Savannah (Passerculus sandwichensis),
grasshopper (Ammodramus savannarum) and Henslow's (A. henslowii)
sparrows, and the bobolink (Dolichonyx oryzivorus). Other species may
be area sensitive as well, but the data are ambiguous. Area sensitivity
among wetland birds remains unknown since virtually no studies have
been based on solid methodologies. We need further research on
grassland bird response to habitat that distinguishes supportable
conclusions from those that may be artifactual.
Key Words: birds, fragmentation, grasslands, habitat, wetlands, wildlife
Diverse and Contrasting Effects of Habitat Fragmentation
George R. Robinson,
Robert D. Holt,
Michael S. Gaines,
Steven P. Hamburg,
Michael L. Johnson,
Henry S. Fitch and
Edward A. Martinko
Department of Biological Sciences, Rutgers University, Piscataway, NJ 08855
Department of Systematics and Ecology and Museum of Natural History, University of Kansas, Lawrence, KS 66045
Department of Systematics and Ecology, University of Kansas, Lawrence, KS 66045
Department of Systematics and Ecology and
Environmental Studies Program, University of Kansas, Lawrence, KS 66045
Science 24 July 1992:
Vol. 257 no. 5069 pp. 524-526
DOI: 10.1126/science.257.5069.524
Abstract
Different components of an ecosystem can respond in very different ways
to habitat fragmentation. An archipelago of patches, representing
different levels of fragmentation, was arrayed within a successional
field and studied over a period of 6 years. Ecosystem processes (soil
mineralization and plant succession) did not vary with the degree of
subdivision, nor did most measures of plant and animal community
diversity. However, fragmentation affected vertebrate population
dynamics and distributional patterns as well as the population
persistence of clonal plant species. The results highlight the dangers
of relying on broad community measures in lieu of detailed population
analyses in studies of fragmented habitats.
DEMOGRAPHIC EFFECTS OF HABITAT FRAGMENTATION ON A TROPICAL HERB: LIFE-TABLE RESPONSE EXPERIMENTS
Emilio M. Bruna1,2 and Madan K. Oli1
1 Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, Florida 32611-0430 USA
2 Tropical Conservation and Development Program, Center for Latin
American Studies, University of Florida, Gainesville, Florida
32611-5530 USA
Ecology 86:1816–1824. [doi:10.1890/04-1716]
Abstract
Habitat fragmentation is a leading cause of extinction, with effects
that may be particularly pronounced in tropical ecosystems. However,
little is known regarding the demographic mechanisms underlying changes
in abundance in fragmented landscapes. Using six years of demographic
data collected from >6600 individuals of the Amazonian understory
herb Heliconia acuminata, we calculated population growth rate (λ) in
experimentally isolated 10-ha forest fragments, 1-ha forest fragments,
and continuous forest. We then used life-table response experiment
analyses to elucidate the mechanisms responsible for observed
differences in λ. On average, λ ≈ 1.05 in continuous forest, while λ ≈
1 in both 1-ha and 10-ha fragments. However, while the differences in λ
between 10-ha fragments and continuous forest were largely attributable
to the negative contribution of stage-specific fertility rates, reduced
λ in 1-ha fragments was due to both reductions in reproductive rates
and changes in the rate of plant growth. Our results show that similar
reductions in λ in fragments of different sizes can be driven by
distinct demographic mechanisms. Without comprehensive demographic
data, attempts to mitigate the decline of populations in fragmented
landscapes could be unsuccessful because they might be focusing on
inappropriate demographic targets.
Keywords: Amazon, deforestation, Heliconia acuminata, Heliconiaceae,
life table response experiment, LTRE, matrix models, population growth
rate, lambda, sensitivity analysis
Received: November 14, 2004; Revised: November 30, 2004; Accepted: December 1, 2004
SOUNDING THE DEPTHS II: (PDF)
The Rising Toll of Sonar, Shipping and Industrial Ocean Noise on Marine Life
Principal Author
Michael Jasny
Coauthors
Joel Reynolds Cara Horowitz Andrew Wetzler
Project Director
Joel Reynold