1. Habitat loss
and fragmentation
Presented by;
Surendra Bam

2. Contents:
 What is it?
 Why is it so important ?
 What causes habitat loss and
fragmentation ?
 What are its effect?
 So what we can do ?
 Conclusion

3. What is it?
Many times,
natural habitats
show a “patchy”
distribution.
This affects the
organisms that
live there.

4. However, in today’s
world the effect of
anthropogenic habitat
fragmentation is
probably much more
significant.
Equally significant is
the fact that many of
the organisms in these
habitats are not
“adapted” for such
fragmentation.

5. Activities such as “clear-cutting” have
created a mosaic of forested and
unforested areas in many regions that were
once completely covered with forests.

7. • A simplistic
view of
fragmentation
is larger
patches being
broken into
smaller ones

8. Why is it so important ?
 Habitat loss reduces the amount of
habitat and habitat type available
 Thought to be the most important
threat to biodiversity at the moment
 Fragmentation results in the pieces of
habitat increasing in insularity with
larger edges as well as a loss of total
habitat

9. What causes habitat loss and
fragmentation ?
-dams in rivers
-roads in parks
-canals
-power lines
-fences
-fire lands
-other ???

10. Dams as
barriers

11. Roads as barriers

12. Roads as avenues for invasion by humans
and exotic species
Initial road 20 yrs later

13. What are its effect?
A. initial exclusion
B. isolation
C. Island biogeography
D. edge effects

14. Initial exclusion, isolation and consequent
loss of biota

15. Island biogeography
MacArthur and Wilson(1960)
• Since the remaining habitat begins to
resemble an island, the ideas of island
biogeography theory are applied to them.
• On small islands, the number of species
results primarily from the interaction of
two processes: Colonization and Extinction
rate.
• The point at which these two rates are in
equilibrium will determine the number of
species found on the island.

16. Colonization rate
Close island
Colonization rate is a
Function of distance Distant island
From mainland
Number of species
Ex tinction rat e
Extinction rate is a
Function of island Small island
size
Large island
Number of species

17. Colonization rate (Distance)
Close, large island
Equilibrium
Number of species
Extinction rate (Size)

18. Colonization rate (Distance)
Number of species
Equilibrium
Distant, Small island
Extinction rate (Size)

19. • So, what happens if we form an “island” from
an area that was once part of a larger
habitat.
• It will, initially, probably contain more species
than the equilibrium of colonization and
extinction can support.
• This, in theory, would lead to biotic
relaxation.
• Biotic relaxation is simply a decline in the
number of species when a formerly
“connected” region becomes isolated as it
approaches a new equilibrium.

20. National Parks are
habitat islands, and
often show biotic
relaxation. This is
often most pronounced
in the smaller parks.
Mount Rainier National
Park in Washington has
seen a reduction in the
number of mammals
found there from 68 to
37 species.

21. D. edge effects
• One of the best
documented effects of
fragmentation are ‘edge
effects’
• Brings change in species
composition with invasion
of exotic species
• For e.g. Cowbird
parasitism (fragmented
forests of Illinois) may be
significant for 100’s of m
into a forest

22. i) Cowbird removing eggs of host songbird
ii) woodthrush nest parasitized by cowbird
iii) Mother blue-winged warbler feeds cowbird chick
iv) Endangered Kirtland’s warbler - highly parasitized by cowbirds

23. • Predation can also be significantly higher
near the edges as densities and movements
of raccoons, opossums, crows, foxes, jays,
skunks, are all higher.

24. Edge effects: Greater vulnerability to
invasion by exotics

26. • The degree to which fragmentation
affects ecosystems depends on the
relative responses of many different
organisms which may respond differently.
• Habitat loss and fragmentation
Increasingly leading to ex situ breeding
and conservation efforts.

27. So what we can do ?
• The first strategy for minimizing habitat
fragmentation is to avoid sensitive
habitats.
• Another important
concept is to have
corridors between
fragments to allow
the movement of
species.

28. • Combination of techniques to improve
connectivity of isolated habitat areas.
Spanaway Creek, Washington
Roadside Vegetation Fences and Walls

29. Wildlife Underpass
High Bridges to preserve
Wildlife Overpass
riparian ecosystems
Box Culverts Small Culverts

30. • cowbirds - put trapped birds into bags
hooked up to car exhaust for killing
• Solutions - reforestation of deforested
lands to create larger core areas for
songbird breeding

31. Conclusion
• Anthropogenic activities are accelerating the
rate of habitat loss and fragmentation.
• Due to which rate of species extinction is
increasing and much are being endangered
giving threat to biodiversity.
• Therefore, our motto should be to
understand this process and develop various
strategy to mitigate this problem as soon as
possible.