Habitat Degradation – decline in habitat quality, affects many but not all species and disrupts communities, may be temporary;

1. Conservation Biology
Threats to Biological Diversity
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S. R. Maharjan
Asst. Professor
Tribhuvan University

2. Major threats to biodiversity
• Habitat degradation and loss
 Conversion from usable to unusable habitat type
 Severe degradation and pollution
 Fragmentation that can reduce population viability
• Habitat fragmentation
• Over exploitation
 Overexploitation of biological resources
 By hunting, collecting, fisheries, wildlife trade and its
products
• Invasive species
• Anthropogenic climate change
• Pollution
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3. Habitat Degradation and Loss
• What constitutes habitat degradation? When is habitat
“lost”?
• Patterns of habitat transformation on land and in the sea
• Human activities that cause habitat degradation
• Pollution as a form of habitat degradation
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4. Habitat Degradation and Loss
• Habitat degradation and loss is the most serious threat
to biodiversity. It is the primary cause of extinction and
endangerment globally.
• Habitat Conversion/Transformation – It refers to
complete change in community and ecosystem state.
▫ About 83% of earths land surface has been transformed by
human activity
▫ Temperate grasslands, shrublands and savannas have lost
their greatest proportion about 80%
▫ More than 20% coral reefs destroyed
▫ 35% mangroove ecosystems destroyed in last two decades
▫ Three to six times more water is stored in dams
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6. • Habitat Degradation – decline in habitat quality, affects
many but not all species and disrupts communities, may
be temporary;
• •Habitat Loss – extreme change in habitat that usually
adversely affects most or all species, effects longer term
and timespan for recovery is also comparatively long
• 83% of Earth’s surface has been transformed by humans
• 60% ecosystems are considered degraded or
unsustainably used
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7. • Habitat degradation and loss are caused by
human activities such as-
 Agriculture, mining, forestry, fisheries, aquaculture,
groundwater extraction,fires, infrastructure
developments,dams, urbanization,industry,
pollution and by invasive species
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Effect of increasing land use intensity on vertebrates and plants in S. America
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Habitat transformations in major Biomes
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12. Patterns of habitat transformation on
land and in the sea
▫ Forest systems and deforestation patterns
▫ Loss and damage to grassland, savanna and
shrub-land habitats
▫ Degradation of freshwater ecosystems
▫ Degradation of marine ecosystems
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13. Patterns of habitat transformations on
land and on the sea
• Prehistoric humans strongly modified the places
they inhabit
• Transformation from forest to agricultural land
can be seen as early as 4000-7000 years B.P.
• Evidence of permanent clearing seen in 1000-
2000 years ago where as clearing from grassland
to cropland can be seen even earlier
• The rate of habitat transformation accelerated
sharply in the last century
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14. • Since 1960s the world population increased to more
than double
• IN US, only 42% of native vegetation remains
• Certain ecosystems such as grassland, floodplains,
wetlands, streams and old growth forests have been
eliminated in 48 states of USA.
• Habitat degradation have been extensive in Europe,
South and East Asia,New Zealand, and coastal
regions near large cities
• Satellite data have been used efficient to analyze
habitat change in forest ecosystems since past 30
years
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15. Patterns of habitat transformation on land and on
the sea-
Forest systems and deforestation patterns
• Forests of the world has been reduced to half
over the past three centuries for cropland,
pastures and settlements
• In 25 countries no forest remains and in
many countries 90% of forests have been lost
• Europe has least forest cover, most of which
were lost before 1700.North American forests
were completely removed by 1850.
• Between 1990 to 2000, the land area covered
by forest decreased from 30.4% to 29.7%,
Africa with highest loss of 8% in a decade
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Natural vegetation degradation in the U.S. based on 1992 satellite image,
change in 58% natural vegetation
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17. Loss of forest cover on
Madagascar between 1950
and 2000 A.D.
Evidence from air photography and remote
sensing suggest that by c. 2000, around 40% to
50% of the forest cover present in 1950
was lost
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21. Indonesia lost 840,000 hectares of forest in 2012 compared to 460,000
hectares in Brazil, despite its forest being a quarter the size of the
Amazon rainforest
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22. • Tropical areas are currently being deforested
at the highest rate (although temperate had
massive deforestation)
• In the Amazon, up to 75% of all rainfall
results from evapotranspiration
• Consequently, deforestation can dramatically
alter climate patterns can change regional
landscapes
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23. • Forests are important because of many
ecosystem services-
 Regulating water supplies
 Controlling erosion
 Affecting climate change
 Over 2/3rd of world population depend on water
flows through forest
The Amazon Basin is the world’s largest expanse of
tropical forest, and despite efforts to reduce
deforestation, rates of forest clearing remain high
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24. • Heavy deforestation increases runoff and cause
flash floods of cities and other settlements.
• Deforestation can also change local, regional and
global climate
• Rate of forest clearing is high in tropical forests
of Amazon Basin
• Forests has shifted from being a carbon sink to
source of CO2 emissions.
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25. Loss and damage to grassland, savanna and shrub-land
habitats
• Grasslands, savanna, and shrublands cover 52.5
million KM2 or 40.5% of Earth’s surface, and are
found predominately in dry subtropical and dry-
humid temperate zones.
• Temperate grasslands have been the most heavily
converted to agriculture and secondarily to urban
environments.
• In N Am, 97% of tallgrass prairie, 60% of mixed- and
short-grass prairie converted since the mid-1800’s
• Over 20% of tropical- subtropical grasslands have
been replaced by agricultural lands.
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26. • Livestock have been raised in grasslands and
savannas
• Extensive fencing in grasslands increase soil
erosion , which also change or eliminate
vegetation.
• Due to climate change and human action,
grasslands, woodlands and marshlands were
transformed into scrublands and deserts.
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27. Degradation of freshwater ecosystems
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28. Degradation of freshwater systems
• With agricultural and urban expansion, water
systems are degraded through water
diversions, dams, and extensive wetland
losses
• Presently, only 2% of US rivers run
unimpeded (<1/3 worldwide).
• In Europe loss of wetlands is 60-70%.In
developing countries, wetland habitats are
affected by dams for irrigated agriculture.
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29. • Water degradation contributes to endangerment for 91% and 99%
of US federally listed fish and mussels, respectively
• In 1970 s a flood plain in Cameroon was dammed for
irrigation.The plain supported abundant fish, birds, mammals as
well as 100000 people.After the dam was built,the ecosystem
collapsed creating biodiversity loss
• Aral Sea, Kazakhstan, once the fourth largest lake in the world.
▫ It has been reduced by 60% in extent over just two decades (Fig. 6.6)
Satellite images taken by NASA in August 2014 revealed that for
the first time in modern history the eastern basin of the Aral Sea
had completely dried upThe shrinking of the Aral Sea has been
called "one of the planet's worst environmental disasters"
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33. Degradation of marine ecosystems
• Almost 60% of world’s population lives within
100km of a coast and as a result, 20% of
ecosystems adjacent to the oceans have been
highly modified
• Many population are dependent on marine
resources for food and income
• Marine ecosystems are degraded by-
▫ Toxic chemicals,solid waste, nitrogen enrichment
▫ Coastal estuaries have been destroyed through
filling, draining, shoreline stabilization and
aquaculture
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34. Degradation of marine ecosystems
• Major rivers such as the Nile, The
colorado,and the Ganges are heavily dammed
for irrigation
▫ Dams and diversion have disturbed the
nutrients and food webs in estuaries
• Mangroves provide nursery and breeding
grounds for fish and invertebrates, as well as
buffer against coastal erosion
▫ Mangroves are being transformed for
aquaculture of shrimp, shellfish, logging of
timber, settlements
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36. • Degradation of marine ecosystems
• Other coastal habitats such as peat swamps of
Vietnam areas suffer from too much
sedimentation or nutrients loading.
• seagrass beds have largely been destroyed
through sedimentation.
• Coral reefs ecosystems are also threatened due
to sedimentation, pollution, recreation, collection
and fishing
• Marine trawling has also led to damage of marine
benthic habitats
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Historical loss of wetlands by state in US- 1960 to 1980s.
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40. Human activities that Cause Habitat
Degradation
• Agricultural activities, extraction and
development are the 3 big drivers in habitat
degradation
• Also main causes of loss of biodiversity
including birds and amphibians
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41. • Agricultural activities (crop and livestock
farming, timber plantations, and aquaculture),
extraction activities (mining, fisheries,
logging, and harvesting) and development
(human settlements, industry and associated
infrastructure) are the three main proximate
causes of habitat degradation and loss.
• In addition habitats are degraded by pollution
and species invasion.
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42. • Causes of Habitat Degradation (Agriculture)
• Agricultural expansion has been the primary
cause of ecosystem change
• Acceleration due to mechanization
• The ‘Green Revolution’ expanded the intensity
with which crops are grown
• In 1700 265M ha to 1.2B ha in 1956, now 5
billion hectares
• Now grow 0.3% annually
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44. • Causes of Habitat Degradation(Ag)
• Other impacts of industrial farming include
high irrigation,fertilizers, heavy pesticides,
herbicides, and pesticides; all of which
negatively impact biodiversity
• Shifting cultivation cause long term
degradation of tree diversity
• Overgrazing has damaged pasturelands
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46. Extractive activities
• Activities such as mining and quarring have
impacts on native habitats and soil disturbances
• Nearly 60% of IUCN Red list plants are
threatened by mining or logging.
• Exploitation of oil and gas and petroleum
refining lead to wide scale habitat degradation.
• Logging cause local extinction of species
• Fisheries have impacts on marine ecosystems
• Use of explosives or cyanides in coral reefs have
devastating impacts on local biodiversity
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47. Urbanization and Development
• Urban expansion frequently comes from
arable land
▫ E.g. China, 5M ha of agriculture were converted
to urbanization from 1987-92
• Waste is high correlated with population
density
• Coastal degradation is also highly correlated
with urban density
• E.g. altering hydrological flows, extraction
• Urban environments also impact on
freshwater systems,and pollute by waste
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48. • War and Violent Conflict
• Obviously war can have long-lasting and
severe impacts on the landscape
• Africa has had many problems and as people
get forced to live in the bush where they
need firewood and they eat animals or poach
for others
• War in Afganistan damaged ecosystems for
two decades
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49. • T
• Thank you
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