Damage caused by invasive species hits the economic performance of developing countries more severely than developed countries, due to their high reliance on agricultural systems. The global cost of this damage has been put at US$1.4 trillion per year – close to 5% of global GDP. In South Africa, India and Brazil the cost amounts to 96%, 78% and 112% of agricultural GDP respectively .
Impact on crops
Invasive diseases and insects attack crops while invasive plants smother them and can significantly reduce the size and viability of arable land. These invasive plants can make field preparation and ploughing difficult, limit the availability of water for crop irrigation, and stop plants from establishing and growing.
In regions where cattle herds represent the primary source of family wealth, plants can invade pasture lands, preventing grazing and poisoning livestock.
The costs associated with controlling the encroachment of pests and weeds, for example by chemical spraying or employing labour to clear invaded land, can be huge. Weeding is done by family members on many farms, taking up time they could be spending on other livelihood activities. Some farmers and ranch-owners are forced to abandon their land as it becomes non-viable, resulting in loss of employment for local workers.
Serious plant infestations can block key transport and trade routes – stopping villagers from getting to the local market where they sell their goods, for instance – and even hit the economy by making an area less attractive to tourists. The presence of invasive pests and diseases, meanwhile, is a barrier to the selling of produce in overseas markets due to quarantine regulations.
Invasive species can also prevent a nation from realising the benefits of investment made in development and infrastructure – aquatic weeds choke irrigation canals and hydroelectric schemes, for example, while invasive mussels foul industrial pipelines.