Module 1: about invasive species

1. Economic Analysis of Invasive Species Module 1: about invasive species

2. what this module covers • Understanding invasive species - a biological and development issue • Movement and introduction of invasive species • Types of organisms that can become invasive • Linking invasions to other environmental pressures about invasive species Module 1 economic analysis of invasive species Module 2 impacts of invasive species and ways to address them Module 3 defining invasive-relatedcosts & benefits Module 4 valuing ecosystem impacts Module 5 informing actionsto address invasives Module 6

3. What are alien invasive species? and why do we care about them enough to have a training course on invasive species for economists??

4. Some definitions: An alien species is a species that has been introduced to a location (ecosystem or area) where it does not occur naturally An alien invasive species (IAS) is an alien species that causes (or has the potential to cause) harm to the environment, economies and/or human health Can you have an invasive species that is not alien?? The change in status from a native species in a stable ecosystem to an invasive species is always accompanied by some change that makes the invading species “different” or “alien” – mostly by being introduced, but sometimes because the ecosystem itself changes Thus we sometimes use the term “invasive species” (IS)

5. Invasions by Alien Species Steps in the progression to invasion: 1. Introduction – intentional or unintentional 2. Establishment – survives but doesn’t spread 3. Spread: 3a. Naturalisation – becomes part of the flora/fauna of its new habitat 3b. Invasion – expands and impacts on species and ecosystems and people and development Probability = 10% (2) x 10% (3a) x 10% (3b) = 0.1% i.e. only 1 in 1000 introduced species ever become invasive – usually less, some say 1 in 1,000,000

6. “Intentional Introduction” “Unintentional Introduction” 1. INTRODUCTION Introductions are mostly due to human activity and can/may result in establishment For food, agriculture, forestry, horticulture, decoration, etc., Species that move with other imports

7. 2. ESTABLISHMENT A plant or animal enters a new environment or habitat or country and survives in the wild – without human help (such as horticulture, aquaculture, aquarium support or domestication). e.g. Many “low-level weeds” and accidentally introduced invertebrates Ornamental canna established Wild canna established

8. 3. SPREAD3a. NATURALISATION The established animal or plant starts to reproduce without assistance and the young survive and begin to spread European birds naturalised in Australia South American Senna spectabilis in Africa begin to regenerate independently after decades or centuries of establishment

9. Wild canna (Canna indica) naturalised as a weed and spreading in Eastern Africa Naturalisation can be equated with “escape from human care”

10. 3. SPREAD3b. INVASION The established and naturalised species spreads and “gets out of hand”, competing with native (and other established) species, Impacting ecosystems and causing environmental damage and/or impacts on human welfare and development Australian possums invaded NZ Latin American Green Apple Snail invaded Asia

11. 1. Introduction 2. Establishment 3a.Spread - Naturalisation 3b. SPREAD - INVASION The House Sparrow spreading and invading Tanzania over 90 years

12. Steps to invasion: Once introduction, establishment and naturalisation have occurred there is often a “lag time” before further spread and invasion 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 As the invading species consolidates, so its affected plant or animal habitats decline or become degraded

13. Habitat occupation changes during invasion Process of Invasion from Introduction to Consolidation (after Williams, 2003) Introduction Invasion Consolidation

14. 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 We will discuss these options in Module 3

15. Movement and Introduction of Invasive Species Vectors: means by which invasives species are moved cars, trucks, buses, aircraft, boats, ships, people, clothes, suitcases, boxes, containers .. »»and: flowing water, tides, storms, floods, winds…. There are six million steel containers moving around the world at any one time

16. Movement of Invasive Species Pathways: routes along which invasive species are moved or move themselves • roads, railways, air corridors, shipping lanes, travel routes, trade routes, migration routes, rivers, ocean currents, … Causes of the movement of invasive species include: • “The 4 T”s: Trade, Travel, Transport, Tourism • All of these have increased many thousand times in the last century due to increasing globalisation– thus spreading species around the world and facilitating their introduction to “new” countries and areas where they are alien

17. Shipping routes now reach every continent (even Antarctica) and air travel reaches most cities in the world

18. Introduction of species The movement (by human action) of a species outside its native range can result in introduction. This movement can be either within or between political boundaries Some establish, naturalise and spread Some establish, naturalise and spread

19. Invasive taxa (types) • Invasive species can animals, plants or micro-organisms (including those causing disease in plants, animals and people) • They can be terrestrial, aquatic or marine • They can be pathogens, parasites or predators • They can be minute, small, large – as well as widespread or locally abundant Some examples from Eastern and Southern Africa follow:

20. Micro-organisms such as: Plant and animal viruses, bacteria, yeasts, Fungal pathogens of both animals and plants • Invertebrates such as: Molluscs (both terrestrial and aquatic) Insect pests Crustaceans Other arthropods …………

21. Argentine Ant spreading in SA Greater Grain borer from Southern USA now widespread Australian longhorned tree borer now invades eucalypts in many African countries Louisiana Crayfish spreading across Eastern and Southern Africa

22. Vertebrate invasive species include: fish, reptiles, birds and mammals Nile tilapia was intentionally introduced to many water systems in Africa, Asia and Latin America – with devastating effects Common carp from China is now invasive in waterbodies on four continents including Africa

23. Lantana camara is a classic IAS 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 tsestse flies and rats

24. Prosopis (spp.),Mesquite, from Central America. An alien invasive introduced for agrofrestry, grows well in dry (pastoral) areas Causes wounds with its spines, replaces native dryland vegetation and destroys pastures for livestock and wildlife

25. “Invasiveness” of Alien Species • What makes a good invader? • Rapid growth rate • Great dispersal characteristics • Large reproductive capacity • Broad environmental tolerance • Effective competitor with local species Lianes in Seychelles All invasive plants can be called “weeds” BUT: Not all weeds are invasive species

26. Finally: 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