MODULE 2

Impacts of IAS

Learning Outcomes

• By the end of this module you should be able to:

– understand the different types of impacts

– know the costs associated with IAS

– give examples of problematic species

– identify the indirect effects of IAS

Categories of IAS impacts

• Economic

• Environmental

• Social

Economic impacts

• In the US the economic costs of invasive plants and animals are estimated at US$137 billion per year.

Economic impacts

• These include:

– Primary production

– Trade

– Infrastructure damage

– Management

– Other sectors

Primary production

• Agriculture

– up to 40% of global agricultural production lost due to IAS

– up to 49% of production in Africa

Primary production

• Leafy spurge

– competes with native plants

– increases erosion

– toxic to animals

– causes skin irritation

Primary production

• European rabbit

– annual cost to Australia’s agricultural production is US$373 million

– feeds on many crops, including wheat and livestock forage

– causes erosion

Primary Production

• Field rat

– Feeds on harvested grain and destroys crops

– In Indonesia consumes 17% of rice crop

Forestry

• IAS impacts include:

– timber losses

– cost of herbicides and pesticides

– worldwide cost of $100 billion per year

Primary Production

• European gypsy moth

– causes extensive defoliation

– eats the leaves of approximately 500 plants and trees

– a major pest in North American forests

Primary Production

• Comb jelly

– comprises up to 95% of the biomass in the Black Sea

– was responsible for the collapse of the anchovy fishery, which was worth $US 250 million/year

Primary Production

• Sea lamprey

– predate upon sport fish in the Great Lakes of North America

– extract blood and fluids from host fish

Trade

• Export restrictions for IAS infested countries

• Hawaii

– loss of millions of dollars in fruit exports when fruit flies discovered

Tourism

• Siam weed (Chromolaena odorata)

– a threat to conservation and ecotourism

– invades natural areas

– reduces biodiversity

– compromises game-viewing in nature reserves and national parks

Tourism

• SARS outbreak

– caused $17 billion loss to China’s tourism industry in 2003

Property / Infrastructure

• Brown Tree Snake

– causes $US 1-4 million damage to power lines on Guam

– power outages every 3 days on average

Property / Infrastructure

• Zebra mussel

– clogs water intakes and discharge pipes

– competes with native mussels

– cost of control is $US 10 billion over 10 years

Fouled pipe

Property / Infrastructure

• Formosan subterranean termite

– infestations weaken the structure of houses

– cause $US1 billion/year of damage in the United States

IAS Management

• Globally, billions of dollars are spent to prevent, eradicate and control IAS impacts

• Although the costs of prevention are often high, they are minor compared to the costs if an IAS were to become established

Social Impacts

• Human health

– introduced infectious diseases can have a devastating impact

– AIDS, smallpox, cholera

AIDS ribbon Smallpox Cholera

Social Impacts

• Recreation

– invasive plants interfere with recreational activities in parks and protected areas

Culture

• Invasive species can impact on the cultural values and activities of an area

• Examples:

- loss of native grasses used in basket making

- the loss of species harvested for ritual

Livelihoods

• Loss of biodiversity due to IAS affects peoples’ livelihoods

Mile-a-minute weed overgrowing a fence in Palau

Environmental Impacts

• Ecosystems and biodiversity

– within an ecosystem all species are connected

– a disruption to one species can affect a whole range of other species

Species level impacts

• IAS can affect native species by:

– changing their abundance

– changing their geographical range

– causing local or global extinction

Ecosystem level impacts

• IAS can change the balance and structure of ecosystem

– common wasps have invaded New Zealand beech forests

– they monopolize high-energy honeydew produced by scale insects

– native species are unable to feed on this important resource

Wasp feeding on honeydew

Processes

• Predation

• Herbivory

• Disease (pathogens)

Black petrel killed by feral cat

Processes

• Physical processes (fire regimes, nitrogen cycles)

• Competition

• Hybridisation

• Parasitism

The mallard duck hybridises with many native duck species

Concluding remarks

• Many IAS are detrimental to the economy as well as human health and the environment

• Unlike other environmental ‘pollutants’ IAS have an increasing impact over time

Summary

• Invasive Alien Species have had enormous negative impacts.

• IAS are found in nearly every habitat and occur in all major taxonomic groups.

• Invasive species can have adverse economic, social and ecological impacts.

• Billions of dollars are spent annually to prevent, control and manage IAS.

• The introduction of an IAS can cause major ecosystem changes.