The Invasive Species

Context:

general principles

Geoffrey Howard

IUCN Global Invasive Species Coordinator

IUCN Nairobi, Kenya

Workshop on biofuel production and invasive species, IUCN Wasaa, Nairobi, Kenya, 20th to 22nd March, 2009

Q: What are invasive alien species?

A: Biological entities that come to a new area

and cause ecosystem degradation

•! 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!)

There are many different terms and definitions in this complex (and

sometimes disputed) area – so we will use the following general definitions:

introductions are nothing new...

...but globalisation

has led to massive

expansion of

opportunities for

introductions

Natural movement

of species has

been going on for

thousands of years

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

2. Establishment

3. Spread

1. Introduction – intentional or unintentional

– survives but doesn’t spread

(a) naturalisation – becomes part

of new habitat’s flora/fauna

(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

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 P

op

ula

tio

n

siz

e

Time

Carrying capacity

Lag

phase

Invasion

Introduction

Process of Invasion from Introduction to Consolidation

(after Williams, 2003)

Introduction Invasion Consolidation

habitat occupation changes during invasion

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

Some establish,

naturalise and spread

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

intentional introduction

unintentional introduction

for food, agriculture,

forestry,

horticulture,

fisheries, hunting,

ornamental and for

pleasure ...

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

Lantana replaces

native vegetation

and pasture, is

poisonous to

livestock and

harbours tsetse

flies and rats

Intentionally

introduced from tropical America

for its flowers, it is now spread by

birds and small

mammals

an example of spread and invasion impacts

In 1974 there was an occasional plant of

Mimosa pigra on the edges of the Kafue River

Kafue Floodplain, Zambia, dry

Kafue Floodplain flooded

1974

1974

The Kafue

Floodplain

was home to many wild

animals and

plants + cattle

grazing,

fishing, conservation

& tourism

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

…. and excluding almost

every other plant and

most animals …. as well

as fisheries, tourism…

2007

2007

Invasion impacts – human development

Water hyacinth affecting Kafue Gorge Dam and hydropower station, Zambia (photo M. Mumba)

Introduced

from tropical America for its

flowers

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

parasitism, pathogenesis,

predation, competition, exclusion and destruction of

productive systems are all

recorded – most known from

farming, horticulture and

livestock production Tall trees of Senna

spectabilis from S.

America replacing

native forest in

Uganda

“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

Arne Witt will enlarge on this topic

all invasive plants can be called “weeds”

BUT not all weeds are invasive species

Invasive lianes from

Asia in Seychelles

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

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

Parties to “prevent the introduction of, control or eradicate

those alien species which threaten ecosystems, habitats or

species” (Art.8(h))

Convention on Biological Diversity

1992 (CBD)

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)