IDB has a clear policy against supporting projects that may introduce invasive species. While on its face this is a logical, clear-cut policy, it can become complex upon implementation.
What exactly are invasive species, and how can the Bank follow both the spirit and letter of this policy?
An invasive species is defined as any species that causes problems for the environment, economy or health due to its ability to spread and become dominant. A native species can become invasive, although the term is more commonly associated with non-native “alien” or “introduced” species.
Invasive species tend to carry a negative connotation: Mediterranean fruit flies devastate citrus plantations, rainbow trout and tilapia are voracious predators of native fish, eucalyptus trees turn areas into deserts and increase wildfires, slash pines invade the native scrub, water hyacinth blocks water channels making navigation impossible, and iceplants cover sand dunes along the coast. The list could go on and on.
Upon closer consideration, however, these same species offer their own advantages. Many of the characteristics that allow an invasive species to become dominant can also be useful in development projects – they are often able to survive under a wide range of conditions, they don’t need much care, they grow fast and are cheap to produce. Trout and tilapia are important sources of protein; eucalyptus and pine are used for wood, pulp and resin; water hyacinth is often used ornamentally in fish ponds; and the ice plant helps stabilize slopes and degraded areas.
Invasives can also change the interactions between species, leading to complex outcomes. Take, for example, the guava. When it escapes from cultivation, it can become a very invasive shrub, and large parts of Galapagos are now covered in guava forest. Giant tortoises, the emblematic species of the island, love the non-native guava, even more than native fruits. In eating it, they carry the seeds in their gut for months before depositing them via manure, perfect for germination. As the tortoises help to disperse the seeds, securing dinner in the future, they are also inadvertently changing the structure of the native forest, so that the endemic guava and other species become rarer, and the unique structure of the forest disappears.
IDB policy states that ‘…the bank will not support operations that introduce invasive species’. However, IDB supports the development of eucalyptus and pine plantations and funds trout and tilapia fisheries. On its face, this would seem to go against the policy, but the truth is different in practice. That is because we have to consider the risks of invasion case-by-case, by carrying out a risk assessment and by being realistic. For example, a sterile eucalyptus cultivar planted in an area with abundant rainfall is unlikely to cause any environmental impacts, and the introduction of tilapia into a river that already has tilapia and flows directly into the sea will also have a low additional impact on the environment.
If there isn’t enough information to make a decision, we should look for solutions that use sterile cultivars or hybrids, or – even better – find an alternative by using a native species. In addition to intentional introductions, we must be very careful not to introduce anything inadvertently (by using contaminated soil, ballast water, or dirty equipment, for example). This is especially important when working in areas that are pristine or highly susceptible, such as offshore islands.
Damage caused by invasive species represents one of the biggest threats to nature and ecosystem services. IDB’s policy reflects this risk. By carrying out project-specific risk assessments, we not only ensure that IDB is not responsible for any damage, but also allow for development projects to continue, providing positive outcomes for both the environment and development.
Written in response to a recent article in the Economist “Invasive Species: Day of the Triffids“