Habitat loss and fragmentation

Presented by;Surendra Bam

Contents:

What is it?Why is it so important ?Why is it so important ?What causes habitat loss and What causes habitat loss and

fragmentation ?fragmentation ?What are its effect?So what we can do ?So what we can do ?ConclusionConclusion

What is it?

Many times, natural habitats show a “patchy” distribution.

This affects the organisms that live there.

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.

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

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

Why is it so important ?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

What causes habitat loss What causes habitat loss and fragmentation ?and fragmentation ?

-dams in rivers -roads in parks -canals -power lines -fences -fire lands -other ???

Dams as barriers

Roads as barriers

Roads as avenues for invasion by humans and exotic species

Initial road 20 yrs later

What are its effect?

A. initial exclusion

B. isolation

C. Island biogeography

D. edge effects

Initial exclusion, isolation and consequent loss of biota

Island biogeographyMacArthur 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.

Close island

Colo

niz

ati

on

rate

Distant island

Number of species

Colonization rate is aFunction of distanceFrom mainland

Exti

nct

ion r

ate

Number of species

Exti

nct

ion r

ate

Number of species

Large island

Small islandExtinction rate is aFunction of island

size

Close, large island

Colo

niz

ati

on

rate

(D

ista

nce

)

Number of species

Exti

nct

ion

rate

(S

ize)

Equilibrium

Distant, Small island

Colo

niz

ati

on

rate

(D

ista

nce

)

Number of species

Exti

nct

ion

rate

(S

ize)

Equilibrium

• 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.

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.

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

i) Cowbird removing eggs of host songbirdii) woodthrush nest parasitized by cowbirdiii) Mother blue-winged warbler feeds cowbird chick iv) Endangered Kirtland’s warbler - highly parasitized by cowbirds

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

i) Racoon feeding on songbird eggsii)Blue jay plundering oriole nest

Edge effects: Greater vulnerability to invasion by exotics

• 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.

So what we can do ?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.

• Combination of techniques to improve connectivity of isolated habitat areas.

Spanaway Creek, Washington

Roadside Vegetation Fences and Walls

Wildlife Overpass

Wildlife UnderpassHigh Bridges to preserve

riparian ecosystems

Box Culverts Small Culverts

• 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

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.