Module 3: Impacts of invasive species and ways to address them Economic Analysis of Invasive Species

what this module covers about invasive species Module 1 impacts of invasive species and ways to address them Module 3 understanding the economic causes of invasions Module 2 defining invasive-related costs & benefits Module 4 valuing ecosystem impacts Module 5 informing actions to address invasives Module 6 1.Understanding the impacts of invasive species 2.Types of impacts of species invasions 3.Prevention of biological invasions 4.Managing invasions 5. Ecosystem restoration after invasion

Invasives threaten *terrestrial, *freshwater & *marine ecosystems with increasing or continuing impacts Invasives will have increased impacts with increasing climate change invasive species impacts on ecosystems

general impacts of IAS Invading species affect ecosystems by altering or replacing natural systems through: competition, exclusion, predation, parasitism, pathogenesis, Alteration of: micro-climate, nutrient availability, ecosystem cycles (energy, water, minerals, organics) – affecting: Ecosystem function, health, goods and services livelihoods, well-being, health, development

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 The Kafue Floodplain was home to many wild animals and plants + cattle grazing, fishing, conservation & tourism

Mimosa pigra continued 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 After a slow start in the late 1980s, M. pigra began to spread By 2000 it was covering a few hundred hectares 2001

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 …. 2007

Mimosa pigra continued Today: No livestock No fisheries No tourism on this part of the Kafue Floodplain Costs to livelihoods and production 3,000 ha of an available 12,000 ha are now covered

examples of invasion impacts Old World Climbing Fern (Lygodium microphyllum), smothering bald cypress in Florida terrestrial impacts

examples of invasion impacts The Indian House Crow (Corvus splendens) has invaded most coastal cities in Eastern Africa kills domestic and wild birds, spreads human diseases, raids food, destroys radio aerials, etc. terrestrial

freshwater Aquatic invasive plants foul drinking water, reduce fisheries, exclude other biodiversity, block waterways and water pipes, reduce oxygen, reduce sunlight… Red Water Fern, Azolla filiculoides from South America – becoming widespread in Africa

freshwater Freshwater fish Introduced for aquaculture, escape into wild water systems, destroy vegetation and fish faunas and hybridize with local species – but benefit to some! Nile tilapia, Oreochromis niloticus, far from the Nile in Zambia

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

impacts on marine systems Such as: fish crabs oysters prawns barnacles mussels comb jellies seaweeds plankton competition, exclusion, predation, fouling Seaweed (Caulerpa taxifolia) invading a new site in the Mediterranean – D. Luguet, France

invasion impacts – human development Water hyacinth affecting Kafue Gorge Dam and hydropower station, Zambia ( photo M. Mumba )

invasion impacts – human development e.g. water hyacinth: Increases water loss in dams Blocks water flows Jams hydropower generators Prevents water traffic Encourages snakes, crocodiles, etc. Suppresses fisheries and aquaculture Harbours vectors of human diseases and there are invasives that are themselves human pathogens – e.g. ebola, SARS, H5N1, etc.

management of invasions To avoid or lessen the impacts of invasion, it makes sense to take one of the following courses of action: 1.Prevent their introduction 2.Eradicate a new invasion soonest 3.Contain a small, expanding invasion 4.Manage the impacts and the presence of an established invasion The CBD tells us that No.1 is best and cheapest; No. 4 is “the last resort” – all have costs

prevention of invasions Prevention is best done by stopping the introduction of likely invasive species – at the end of a pathway ( module 1 and pathway types ) This requires a means to stop introduction, e.g. border inspections, quarantine, and a method to assess likely invasibility Rigorous Risk Assessment can identify species that may become invasive in the intended area or ecosystem – then they can be stopped Prevention of establishment, naturalisation and spread, once a species is introduced is possible in some cases, but more costly, needing capacity for “rapid response”

management/control of invasions “Management” is required once a species has established an invasion and the impacts are becoming obvious and need to be reduced or removed = controlled There are 4 main types of IAS control: Mechanical Chemical Biological control (biocontrol) Integrated control involving two or three Management requires agreed objectives by stakeholders to ensure successful results

mechanical control Clearing, cutting, catching, trapping mechanically – by hand or with tools and traps or, sometimes with heavy and sophisticated machinery Little non-target impact but often not sustainable – especially in plants with significant seed banks Mechanical clearance of Lantana camara by hand

chemical control As the name implies, this involves herbicides, poisons, pharmaceuticals, hormones (and pheromones), or any other chemicals that can reduce the population or vitality of invading micro-organisms, plants or animals Chemical control has to be cautious to lessen the risk of affecting non-target organisms and polluting the environment – but can be very effective in some cases While complete eradication of small invasive animals on islands has been effected with poisons, this method has drawbacks associated with dosages and applications in the field – especially on organisms that are not well-known

biological control Many invading species are able to invade because they have come to a new ecosystem without their native control organisms such as parasites, pathogens and predators Biocontrol seeks to fill that void by using organisms from the invaders original “home” where it was “held in check” Such organisms are tested for species specificity, introduced through quarantine, bred in large numbers, released on or near the target invasive species …. … and left to carry out control (with monitoring to measure survival, spread and success) Biocontrol of agricultural invaders are best known – as are the insect control agents for invading water hyacinth

integrated control This is a combination of control measures designed to make the most of the benefits of each method For example, effective biocontrol can weaken the ability of an invading species to complete with local biota. If this is combined with mechanical and chemical control to stop expansion, or to manage critical habitats, the overall effect can be beneficial to the invaded ecosystem – as well as becoming self- sustaining

but all control has costs: Photos by Griffin Shanungu, Pilot site coordinator, Barriers project, Zambia Mechanical clearing and burning of Mimosa pigra on the Kafue Floodplain (discussed earlier) 40 field workers worked for 17 weeks to clear 31 ha of mimosa for a total cost of $34,250 – invasion is 30,000 ha

benefits of invasive species Some biological invasions bring benefits as well as costs – to local people and development, e.g. Water hyacinth can be used for biogas, compost, stock food, furniture Mesquite can reduce erosion, produce timber and charcoal Lantana stems are used for chicken cages Australian rabbits can be eaten – as well as feral pigs and goats But it is rare that the benefits exceed the costs or can pay for the necessary control

ecosystem restoration Amongst the objectives for invasive species management, there is often a wish to return the affected system to its original status This requires a set of actions together referred to as ecosystem restoration – including:- returning lost species, understanding biological succession, and, addressing needs of stakeholders The use of other potentially invasive species should not be used – even if it can speed up the restoration!

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