Economic Analysis of Invasive Species

Exercise 2, Module 2: understanding the economic causes of invasions

Time allocated to the exercise: 25 minutes small group work

25 minutes report-back plenary discussion

Exercise 2

Divide into three groups (you will each be allocated to a group):

  1. the invasive fishes: The Nile Tilapia was introduced in 1999 to Lake Geoffrey by the International Organisation for the Promotion of Export Business (IOPEB), as part of a project which aimed to promote aquaculture as a means of income generation for local fishermen, and to increase the production of fish for the export market. Fingerlings were distributed to the owners of aquaculture ponds, who fed them and maintained them to saleable sizes. There were inevitable escapes from fishponds into the lake system. Over the last 5 years, populations of Nile Tilapia have become invasive in Lake Geoffrey, consuming other smaller fish, invertebrates and aquatic plants – impacting on the breeding, food sources and productivity of fish species which are important for local subsistence and income. The Nile Tilapia has had devastating impacts on the biodiversity of Lake Geoffrey.
  2. the invasive agricultural weeds: The seeds of the weed Parthenium were inadvertently introduced via consignments of imported grains from North America, which were imported and distributed by a foreign aid agency as part of a nutrition improvement programme in the Republic of Nchi. The Parthenium has now spread into surrounding farms, affecting the production of grains and vegetables, and has also impacted on livestock production by tainting the milk of the cows. The pollen of Parthenium also causes dermatitis and asthma in humans.
  3. the invasive environmental weeds: Prosopis was introduced by the government of Aridland to reduce erosion and provide shade in dryland areas which had become degraded due to over-grazing, unsustainable agricultural practices and deforestation. After some years the plants started to spread, and have now become invasive. They are choking off natural vegetation, and thereby excluding people, livestock and wildlife from these mainly pastoralist areas. At the same time, Prosopis is spreading into a nearby National Park.

You are economic analysts advising the Ministry of Finance and Economic Planning about the steps which are necessary to prevent such invasions occurring in other parts of the country.

For the invasive species that your group is dealing with:

a)  First identify the main direct economic cause(s) of the invasion.

b)  Then, identify the underlying economic conditions or motivations which might have prompted people to behave in a way which has led to the invasion taking place.

c)  Finally, list the economic policies and instruments which might have set the particular conditions which have encouraged people to behave in a way which has led to the invasion taking place.

Discuss this in your working groups for 25 minutes maximum, and be prepared to make a brief 5 minute presentation back in the plenary session which describes the direct and underlying economic causes of the invasion you are dealing with.