Module 3:

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Economic Analysis of Invasive Species
Module 3 Impacts of invasive species and ways to
address them
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what this module covers

• Understanding the impacts of invasive species
• Types of impacts of species invasions
• Prevention of biological invasions
• Managing invasions
• Ecosystem restoration after invasion

about invasive species
Module 1
understanding the economic causes of invasions
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
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invasive species impacts on ecosystems

• Invasives threaten terrestrial, freshwater
  marine ecosystems with increasing or continuing
  impacts
• Invasives will have increased impacts with
  increasing climate change

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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
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an example of spread and invasion impacts
The Kafue Floodplain was home to many wild
animals and plants cattle grazing,
fishing, conservation tourism
Kafue Floodplain, Zambia, dry
1974
Kafue Floodplain flooded

• In 1974 there was an occasional plant of Mimosa
  pigra on the edges of the Kafue River

1974
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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
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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
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Mimosa pigra continued

• By 2007 it was growing up to 4m high and covering
  3,000 hectares

2007
. and excluding almost every other plant and
most animals .
2007
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Mimosa pigra continued
3,000 ha of an available 12,000 ha are now covered

• Today
• No livestock
• No fisheries
• No tourism on this part of the Kafue Floodplain

Costs to livelihoods and production
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examples of invasion impacts
terrestrial impacts

• Old World Climbing Fern (Lygodium microphyllum),
  smothering bald cypress in Florida

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examples of invasion impacts
terrestrial

• 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.
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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
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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
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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
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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
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invasion impacts human development

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

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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.
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management of invasions
To avoid or lessen the impacts of invasion, it
makes sense to take one of the following courses
of action

• Prevent their introduction
• Eradicate a new invasion soonest
• Contain a small, expanding invasion
• 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
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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
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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
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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
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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

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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
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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

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but all control has costs
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
Photos by Griffin Shanungu, Pilot site
coordinator, Barriers project, Zambia
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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
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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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THANK YOU for listening