MODULE 1 Introduction to Invasive Alien Species Introduction

MODULE 1 Introduction to Invasive Alien Species

Introduction • Invasive alien species harm: – the environment – the economy – people

Definition • Introduction – The movement by human action of a species outside its native range. This movement can be either within or between countries.

Definition • Alien species – A species that has been intentionally or unintentionally introduced to a location, area, or region where it does not occur naturally

Definition • Invasive alien species – An alien species that causes, or has the potential to cause, harm to the environment, economies, or human health

Key Point • An alien species will be considered invasive only if it has adverse effects on: – the environment, – the economy, or – human health

A m n Fu s ph ng ib ia i In ve rt eb ra te s Re pt i le s P la nt s Fi sh B i rd s M V a i l r s m s u m se a Invasive Species are found in ALL taxonomic groups

Types of introductions Alien Species Introductions Intentional Legal Directly released into the wild Unintentional Unauthorised Introduced into captivity Escaped or intentionally released

Indian House Crow • Accidental introduction • Competes with native birds • Disease vector • A nuisance in urban areas

Salvinia molesta • • A serious aquatic weed Forms thick mats Prevents boat traffic Ruins fish habitat

Intentional introductions • Legal – directly released into the wild – introduced into captivity • Illegal / Unauthorised – smuggling

Unintentional introductions • ‘Hitchhikers’ and stowaways • Trade • Travel • Transport

Key Point • Most of the known invasive invertebrates have been introduced unintentionally

Key Point • Natural dispersal tends to play a major role in the subsequent regional spreading once a species has been introduced into a country or region

Process of invasion 1. Introduction 2. Establishment 3. Spread

Process of invasion Population size Explosion phase Carrying capacity Lag phase Time

Can we predict species invasiveness? • Difficult to identify invasive from harmless species • Some characteristics: – invasive elsewhere – adaptable – lack of predators

Key Point • Precautionary approach Every alien species must be considered invasive until proven otherwise

Key Point • Human alteration of the environment increases the likelihood of IAS establishing

Land-use changes • IAS thrive in disturbed areas

Globalisation • Increasing trade, travel & transport = increasing IAS introductions World shipping routes

Summary • IAS affect the environment, economy and human health • Species invasiveness cannot be easily predicted • IAS thrive in disturbed areas • The rate of IAS introductions is increasing