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Submodule 7: The Price We Pay -- Economic Impacts
How the Cost for Invasive Species is Calculated
Researchers and economists use several different methods to come up with estimates for the costs of invasive species. While difficult, it is important to attribute monetary values to costs for resource losses and for management. Here are a few of examples to give you an idea of how these numbers are generated:
Hydrilla
Rat
Feral cat (photo courtesy NCBI)
Karnal bunt-affected wheat
(photo courtesy USDA-ARS)
Karnal bunt fungus (photo
courtesy USDA)
Hydrilla (Hydrilla verticillata): Florida spends about $14 million dollars per year to control this menacing aquatic plant. Local authorities have estimated lost revenue at two of these lakes exceeds $10 million annually. In Washington State, the Department of Ecology estimates that in the 1990s, hydrilla may have filled approximately 7,500 lakes by late 1993. Whole-lake management costs for a problem of this magnitude could exceed $500,000 per lake, which totals up to $3.8 million. In the early 1990s, hydrilla at Lake Moultrie, South Carolina shut down the St. Stephen powerhouse operations for seven weeks resulting in $2,650,000 of expenses due to repairs, dredging, and fish loss. In addition, during this repair period, there was an estimated $2,000,000 loss in power generation for the plant. In general, researchers and land managers know that treatment of a single acre of water can cost up to $1,000, so by using this number they can calculate the cost of treating infestations by know the number of acres affects.
Rats (Rattus rattus and R. norvegicus) and house mice (Mus musculus): On farms (particularly poultry farms) mice and rats are numerous and destructive; the total on-farm rodent population is estimated as over 1 billion. It is estimated that there is about 1 rat/person in the U.S in homes and other domestic dwellings, for a total of about 250 million. Conservative estimates are that each of these rodents causes about $15 in damages per year. Therefore, 1,000,000,000 mice and rats on farms + 250,000,000 rats in homes and other buildings =
1.25 billion rodents X $15 = $18,750,000,000 in damage costs alone.
Feral cats: There are estimated to be about 30 million feral cats in the U.S. These cats feed primarily on native birds and small mammals. A recent study in Wisconsin and Virginia found that in each state, feral cats kill more than 3 million birds/year or about 8 birds/cat annually. Extrapolated to the entire country, this means that feral cats kill about 240 million birds annually. Based on the literature which calculates the value of each bird at about $30, bird loss from feral cats is estimated at $7 billion. This does not include the value of birds killed by pet cats, or the value of fish and other small animals killed by both.
Karnal bunt (Tilletia indica): Economists at Texas A & M did an analysis of the annual economic costs of karnal bunt in the Rolling Plains areas of Texas (a 4,500 square mile section of the state). Some of the reported losses were:
- More than $3.6 million due to a reduced value as a livestock feed wheat ($1.25 to $1.50 per bushel).
- More than $2.8 million on wheat not eligible for federal compensation.
- More than $1.9 million in interest and storage costs, due to producers not being able to move or sell their affected wheat.
- More than $733,000 for buying new seed or treating negative seed for the 2001-2002 wheat crops.
- More than $1 million from producers switching to other crops.
- More than $1.9 million due to reduced stocker cattle contracts.
- More than $1 million in lost wheat seed cleaning and fertilizer sales for agribusinesses.
These estimates total almost $13 million in Texas alone.
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