Download The Invasive Species Context: general principles

Workshop on biofuel production and invasive species, IUCN Wasaa, Nairobi, Kenya, 20th to 22nd March, 2009
The Invasive Species
Context:
general principles
Geoffrey Howard
IUCN Global Invasive Species Coordinator
IUCN Nairobi, Kenya
Q: What are invasive alien species?
A: Biological entities that come to a new area
and cause ecosystem degradation
There are many different terms and definitions in this complex (and
sometimes disputed) area – so we will use the following general definitions:
•! An alien species is one that is introduced to a new
location (ecosystem or area) where it does not occur
naturally (i.e. non-native, non-indigenous)
•! An invasive alien species (IAS) is an alien species that
causes (or has the potential to cause) harm to
biodiversity, the environment, economies and/or human
health
FROM HERE-ON: we will call them:
“invasive species” = IS (to make life easier!)
introductions are nothing new...
Natural movement
of species has
been going on for
thousands of years
...but globalisation
has led to massive
expansion of
opportunities for
introductions
what types of species invade?
from all taxonomic groups
•! vertebrates (e.g. mammals, fish, birds,
amphibians, reptiles)
•! invertebrates (e.g. insects, crustaceans,
snails, worms)
•! aquatic and terrestrial plants (e.g. ferns,
mosses, herbs, shrubs, trees)
•! micro-organisms (e.g. viruses, bacteria,
yeasts, protozoa, protophyta)
The Process of Invasion
1. Introduction
– intentional or unintentional
2. Establishment – survives but doesn’t spread
(a) naturalisation – becomes part
of new habitat’s flora/fauna
3. Spread
(b) invasion – expands and
impacts on species, ecosystems
people and development
1. Introduction
2. Establishment
3a.Spread - Naturalisation
3b. SPREAD - INVASION
the House Sparrow
(from Asia) spreading
and invading Tanzania
over 90 years
Many IAS undergo a “lag phase” after initial
establishment, and may remain unobtrusive before
becoming invasive and spreading rapidly
Population
size
In some species (e.g. trees) this may be more
than 100 years, in others (e.g. water hyacinth) it
may be a few weeks
Introduction
Invasion
Carrying capacity
Lag
phase
Time
habitat occupation changes during invasion
Introduction
Invasion
Consolidation
Process of Invasion from
Introduction to Consolidation
(after Williams, 2003)
Invasions can thus be
stopped at several stages:
•! best is prevention = stopping introductions
•! next best is eradication = destroying or removing a new
invasion
•! third is containment = stopping a new invasion from
further spreading
•! last (and most expensive and time-consuming) is
management of established invasions + restoration of
affected systems
•! Sequence endorsed under Convention on Biological
Diversity (CBD Guiding Principles for IAS management)
how do species get moved
around?
Vectors: The specific mechanisms by
which a species is moved along a
pathway (clothing, vehicle, boat hulls,
ballast water, packaging, soil around plant
roots...)
e.g. a tourist carrying seeds is a
vector in the pathway of international
airline flights
Pathways: The routes along which a
species is moved or moves itself (roads,
railways, air corridors, shipping lanes,
rivers) ... including trade itself
Shipping routes now reach every continent (even
Antarctica) and air travel reaches most cities in the world
introduction of (alien) species
Movement by human action of a species outside its native range
can result in introduction (into/within a country or ecosystem)
Some establish,
naturalise and
spread
Some establish,
naturalise and
spread
intentional introduction
for food, agriculture,
forestry,
horticulture,
fisheries, hunting,
ornamental and for
pleasure ...
unintentional introduction
species that move
with other imports
as ‘hitchhikers’ or
‘stowaways’
Impacts of Invasive Species
negative impacts on:
•! ecosystems
•! economies
•! human health
Ecological and biodiversity impacts
•! direct predation/herbivory
•! competition for resources/exclusion (e.g. light, food, water, space)
•! transmission of pathogens and parasites
•! alteration of micro-climate, nutrient availability, ecosystem
cycles (energy, water, minerals, organics)
•! disturbance to ecological processes (e.g. pollination)
•! disruption of ecosystem services (e.g. flood attenuation)
•! environmental degradation, facilitating further invasions
economic impacts
estimated at 5% global GDP
Direct costs
•! Direct loss of crops, reduced yields
•! Lost export earnings
•! Loss of tourism revenues
•! Management costs
Indirect costs
•! Impaired ecosystem services
•! Damaged infrastructure
•! Costs to natural environment and
societal or cultural values
health impacts
Direct impacts
•! Disease
•! Allergic reactions
•! Injuries through stinging or biting
•! Poisons
Indirect impacts
•! Providing a vector for disease
Lantana camara is a classic IS which (after 160
years) is still spreading across Africa and
invading new lands - as well as in Australia,
Asia and North America
Intentionally
introduced from
tropical America
for its flowers, it
is now spread by
birds and small
mammals
Lantana replaces
native vegetation
and pasture, is
poisonous to
livestock and
harbours tsetse
flies and rats
an example of spread and invasion impacts
Kafue Floodplain, Zambia, dry
1974
Kafue Floodplain flooded
1974
The Kafue
Floodplain
was home to
many wild
animals and
plants + cattle
grazing,
fishing,
conservation
& tourism
In 1974 there was an
occasional plant of
Mimosa pigra on the
edges of the Kafue River
A heavy flood in 1981/2 brought a few
plants of Mimosa pigra on to the
floodplain
(which was
a new
ecosystem
changed by
a dam
upstream)
1982
Mimosa pigra (continued)
By 2007 it was
growing up to 4m high
and covering 3,000
hectares
2007
2007
…. and excluding almost
every other plant and
most animals …. as well
as fisheries, tourism…
Invasion impacts – human development
Introduced
from tropical
America for its
flowers
Water hyacinth affecting Kafue Gorge Dam and hydropower station, Zambia
(photo
M. Mumba)
Impacts on production (eco)systems
ecosystems, native or cultured,
that are used for food and
commodity production can also
be invaded by alien species
forestry, fisheries, agriculture,
aquaculture
Tall trees of Senna
spectabilis from S.
America replacing
native forest in
Uganda
parasitism, pathogenesis,
predation, competition,
exclusion and destruction of
productive systems are all
recorded – most known from
farming, horticulture and
livestock production
“Invasiveness” of
an alien species
what makes a good invader?
•!rapid growth rate
•!great dispersal characteristics
•!large reproductive capacity
•!broad environmental tolerance
•!effective competitor with local species
Invasive lianes from
Asia in Seychelles
Arne Witt will enlarge on this topic
all invasive plants can be called “weeds”
BUT not all weeds are invasive species
current and future trends
human activities are changing natural ecosystems and
making them more susceptible to IAS
•! globalisation
•! land-use change
•! climate change
invasives and climate change
climate change is upon us - although not exactly
predictable in area or extent
climate change will make ecosystems more vulnerable
to invasions
invasive species are already “taking advantage” of
changed climatic conditions and expanding to the
detriment of local species, habitats and ecosystems
thus we must be prepared for ecosystems affected by
climate change to be further invaded and we must
develop tools to predict and prevent these extra
invasions
causes and effects of Invasive Species are
international or regional
IS management and control is supported by
bilateral, regional and global instruments
and guidance
Convention on Biological Diversity
1992 (CBD)
Parties to “prevent the introduction of, control or eradicate
those alien species which threaten ecosystems, habitats or
species” (Art.8(h))
emerging principles of IAS management
•! the precautionary principle
•! the principle of preventive action
•! the ecosystem approach
•! sharing of information
•! user-pays principle
•! cross-sectoral approach to management
Other instruments and guidance
International Plant Protection Convention
African Convention on Nature and Natural
Resources
NEPAD Environmental Programme
Roundtable on Sustainable Biofuels
Invasive Species Specialist Group of IUCN
The Global Invasive Species Programme
(GISP) www.gisp.org
Sharing of expertise
and information is
crucial
Types of information to be shared?
•!
Inventories and databases
•!
Incident lists and case studies
•!
Potential threats to neighbouring countries
•!
Information on taxonomy, ecology and genetics of IAS
•!
Prevention and control methods where available
•!
National and regional guidelines and measures
Many IAS databases are accessible electronically
EAFRINET
The eastern Africa LOOP of BioNET-International
THANKS FOR YOUR ATTENTION
Ethiopian camel pasture and native vegetation invaded by
two alien species of Opuntia (introduced cactus)