Impacts of IAS
IAS INVASIONS AND AGRICULTURE IMPACTS
In order to understand the impacts of IAS on biodiversity, trade, tourism, agriculture, and specifically food production, it is important to understand the nature of such impacts. In general, impacts of IAS can be understood from three main perspectives – environmental, economic and social. These are explained briefly below. Generally, however, impacts of IAS tend to focus on biodiversity and ecosystem loss.
Environmental Impact
As expected, and by their nature, the initial impact of IAS will be manifest in the destruction or disruption of affected areas and habitats, and eventually, the wider environment. Invasive plants and animals have a devastating impact by outcompeting native species for habitat space and food source. Many small sparsely populated islands and/or areas and regions within countries that are not populated have had their landscapes completely altered by the presence of invasives, such as, feral donkeys, cattle and goats. Christmas bush (Chromolaena odorata), for example, affects the nesting sites of crocodiles, directly placing these populations at risk. Also Bird Life International (BLI) has implicated IAS in nearly half of the recent bird extinctions . Many of these birds are critical to their ecosystems through their contributions to seed dispersal of important native trees. These birds are also an important aspect of the country’s tourism product.
The majority of plant and animal species (95 percent) are affected by introduced predators and are frequently subject to multiple impacts from a range of invasives. Predation by introduced dogs, pigs and mongooses and habitat destruction by sheep, rabbits and goats have been implicated in some cases. However, predation by introduced rats and cats and diseases caused by introduced pathogens, are now recognised as the most deadly cause. For example, the Solenodontidae family (family of small burrowing mammals) includes two surviving but endangered species which are threatened by IAS, such as, mongoose, feral cats, rats and dogs and by human exploitation. The Capromyidae family (family of large cavy-like rodents) is also threatened by invasive species, hunting and habitat loss.
Research published in January 2010 in Biology Letters by Alanx C. et al suggested a strong link between protein nutrition and immunity in bees.( ) Protein nutrition was in turn related to the diversity of pollen sources. Where bees were limited to narrow diversity of pollen sources, such as ecosystems that had greater presence of invasive plants, the immune competence of bees were compromised leading to poor apiary health. This potentially has implication for a wide range of crops that are dependent on bees for pollination. This study demonstrates the intricate link between food crops and biodiversity within a native ecosystem. However, IAS can have other impacts on the economy through effects on agriculture, fishing, forestry, tourism, etc., through structural damage (e.g., zebra mussels in waterways) and through public health issues (HINI virus) and loss of worker productivity.
Economic Impact
As is now being appreciated, environmental destruction comes at a price. IAS-induced destruction of biodiversity will therefore eventually compromise the productive capacity of natural resource dependent industries, mainly agriculture and tourism, two critical economic sectors in all Caribbean countries.
Although it is difficult to quantify economic losses, estimates from Florida indicate approximately US$1 billion in control costs and losses between 1995 and 2001 as a result of newly introduced invasive species affecting agriculture. The average annual spending of the USDA-APHIS on its emergency programs for the period 1989-2002 rose exponentially from about US $6.4 million in 1989 to US $334.8 million in 2001, or about 32.7 percent annually. Concise data on the economic loss caused by IAS in the Caribbean is limited. Losses caused by the PHMB outbreak in Grenada for the period 1995-1998 totalled US$18.3 million. In Trinidad and Tobago, potential losses to agriculture and forestry were estimated at US$125 million. However, successful control considerably reduced this to US$ 5.1 million over the 1994 to 1997 period. Crop losses caused by the PHMB throughout the entire insular Caribbean were estimated at US $138 million, exclusive of the costs of control and export losses . Reappearance of the classical swine fever in Haiti in 1996 took a heavy toll, leading to death of 80 percent of the swine population. Costs of the on-going program of eradication in Haiti and the Dominican Republic have been estimated at $12.1 million.
Some IAS directly threatens the habitat of species that are important to the tourism industry. Water hyacinth, by clogging waterways, affects water-based recreational activities. Species loss also has adverse impacts on tourism. For example in the Seychelles’ Bird Island, where Anoplolepis gracilipes (crazy ant) displaced about 60,000 pairs of Sterna fuscata (sooty terns), tourism was adversely affected .
Social Impact
IAS also leads to adverse health impacts with heavy costs to society. Outbreaks can restrict travel from and to affected areas eg swine flu, disrupt school system (e.g., from outbreaks of rats to H1N1 virus), limit hosting of public events, such as, cultural festivals; affect availability of local foods due to devastation on local agriculture, increase the demands on health systems and significant loss of productive man hours due to ill health.