The document discusses invasive alien species (IAS) as a threat to biodiversity and the environment. It describes how some species have traits like rapid growth and reproduction that allow them to outcompete native species. IAS are often introduced through human activities like importing plants, releasing ballast water from ships, or the pet trade. They can negatively impact ecosystems, economies, agriculture, and human health. Effective control requires integrated approaches like mechanical removal, chemicals, biological controls, and habitat management. The conclusion states that IAS are a major threat globally and that their impacts must be managed.

1. INVASIVE ALIEN SPECIES(IAS):
A THREAT TO THE
BIODIVERSITY AND
ENVIRONMENT
BY
Surendra Bam

2. Outline
 Introduction
 Conditions that lead to invasion
-> Species-based
mechanisms
-> Ecosystem-based
mechanisms
 Pathway of Introduction
 Impacts
 Control and management

3. Introduction
 An Invasive species is an
organism that is not
indigenous/native to its
environment.
 Invasive species can be a
plant, animal or insect.
 Different words are used to
describe species occurring in

4. Introduction
contd..
According to the Global
Invasive Species Program
(GISP):
“Invasive alien species (IAS)
are non-native organisms that
cause, or have the potential
to cause, harm to the
environment, economies, or

5.  Invasion is considered as the
second most important threat to
biodiversity after All Species
habitat
destruction.
Marine Species
Invasive species are so much important in
the present scenario that, article 8(h) of the
Biodiversity Convention asks for measures ‘‘to
prevent the introduction, control or even

6. Conditions that
Two lead to that when combined
mechanisms, invasion
establish invasiveness in a newly
introduced species;
1. Species-based mechanisms
 Invasive species appear to have specific
traits that allow them to outcompete
native species.
 Common invasive species traits include:
-Fast growth, for e.g.Mile-a-minute
weed (Mikania micarantha),i) a fast
Mikania

7. - Rapid reproduction
- High dispersal ability
- Phenotypic plasticity
(the ability to alter growth
ii) Barbed
form to suit current conditions)
goatgrass
-Tolerance of a wide range of
environmental conditions (
Ecological competence), For e.g.
Barbed goatgrass (Aegilops
triuncialis) introduced to California
on serpentine soils (low water-

8. - They are usually generalist.
- Association with humans
- Prior successful invasions
- Ecological facilitation Lantana
iii)
like
alleopathy mechanism. For e.g.
Lantana (Lantana camara).
2. Ecosystem-based
mechanisms
 describe a situation in which the

9. - changes such as a forest fire.
For e.g. Bromus tectorum,
highly fire-adapted. It not only
spreads rapidly after burning
but also increases the
frequency and intensity of
fires, by providing large
amounts of dry detritus.
iv) Bromus v) Water hyacinth

10. - Habitat
fragmentation and
Edge effect, brings change in
species composition with
invasion of exotic species.
vi) woodthrush nest
parasitized by cowbird

11. Pathway of
 Introduction
Non-native species have many
vectors, including many
biogenic ones, but most
species considered "invasive"
are associated with human
activity.
vii) zebra mussel
- Ballast water taken up at sea
and released in port is a
major

12. - Plants or seeds imported for
horticulture.
- The pet trade moves animals
across borders, where they can
escape and become invasive.
- Chinese mitten crab,
introduced viii) Chinese mitten crab
in foreign water for
economic purpose.

13. Impacts
1. Ecological
 Disturbed habitats are prone to
invasions that can have adverse
effects on
local ecosystems, changing
ecosystem functions.
 In the Waterberg region of South
Africa, cattle grazing over the past
six centuries has allowed invasive
scrub and small trees to displace

16.  Invasive species can change the
functions of ecosystems. For
example, invasive plants can alter
the fire regimen (cheatgrass,
Bromus tectorum), nutrient
cycling (smooth cordgrass
Spartina alterniflora), and
hydrology (Tamrix) in native
ecosystems.
2. Economic
a) Benefits

17.  Vegetative invasives such as
water hyacinth can be turned
into fuel by methane digesters.
b) Cost
 Estimated damage and control
cost of invasive species in the
U.S. alone amount to more than
$138 billion annually.
 If monetary values were
assigned to the extinction of

18. 3. Agriculture
 Many introduced weeds in
agriculture field compete
with native crops.
ix) Mikania on banana plants
 A decline in pollinator services and
loss of fruit production has been
caused
by honey bees infected by
the invasive varroa mite. mite
x) Varroa
 Introduced rats (Rattus rattus and

19. 4. Forestry
 The unintentional introduction of
forest pest species and plant
pathogens can change forest
ecology.
For e.g. Mikania micarantha
xi) Mikania covering trees
(Lahare banmara).
5. Health
 Introduced birds (e.g. pigeons),
rodents and insects (e.g. mosquito,

20. 6. Biodiversity
 Biotic invasion is considered one of
the five top drivers for global
biodiversity loss and is increasing
because of tourism and
globalization.
xii) Invasive plant in Rhino xiii) American alligator attacking
habitat a Burmese python in florida.
 Invasive species may drive local

21. Control and
management
xiv) Harvesting vehicles xv) Root talon xvi) weed wrench
1. Physical (Mechanical) control
- It involves directly removing the
species by hand or with
appropriate machines.
- such as harvesting vehicles (e.g.,

22. 2. Chemical control
- Involves the use of
herbicides, insecticides, and
rodenticides that primarily
affect the target species.

23. 3. Biological control
- Intentional use of populations of
natural enemies of the target
invasive alien species.
 For e.g. Mikania is an excellent
example where this new generation
of classical biological control
agents, namely fungal pathogens
are used to control it.
4. Integrated pest management
(IPM) and Habitat management

24. - Habitat management
involves measures such as
prescribed burning, grazing
and other activities.
- Therefore, given the high
complexity of the ecology
of invasive species and
habitats affected, control

25. Conclusion
 Invasive Alien Species (IAS) are the
second greatest threat to biological
diversity globally and the highest
threat on many island ecosystems.
 The adverse environmental impacts
such as alteration of habitat and
species composition have been
experienced due to some alien
species.
 The control and management of

27. References
 Drake, J. A., Mooney, H. A., Di Castri,
F., Groves, R.H., Kruger, F. J.,
Rejmanek, M. and Williamson, M.
1989. Biological invasion: A global
perspective. Scope 37. Wiley,
Chichester, London, England.
 Mooney, H.A. and Hobbs, R.J. 2000.
Invasive species in a changing world.
Island (press,Washington, D.C.)
 Tiwari, S., Adhikari, B., Siwakoti, M.
and Subedi, K. 2005. An inventory