By guest blogger Rebeka Ryvola, Ecologic Institute
When introduced into new environments, invasive species can be a major problem. Invasives – species living in a certain area where they don’t belong – can harm the native species present or out-survive them and cause dramatic ecosystem changes. The changes are usually for the worse.
Humans are often unwittingly instrumental in helping these species infiltrate new territories, and we’re finding more and more evidence that marine debris is a culprit.
Invasive species stage their “invasions” in a number of ways. They can float through the air, travel by water currents, or cling to migrating animals. On land, species such as insects and plants can hitchhike by lurking in suitcases, in and on cars, on bicycles, and even on your clothing. Oceanic species – such as barnacles, mollusks, algae, and fish – can attach themselves to boats or stow away in ship ballast water.
When it comes to the ocean, ships are not the only means of transportation for invasives; efforts to stop these species are challenged by marine debris in our oceans and seas. It turns out that ocean-bound marine litter often offers potential invaders free round-the-world trips to entirely new territories and areas that may not be prepared for the influx of strange and competitive species.
In 2009, researcher David Barnes studied the remote Seychelles Islands and found that over 60 percent of marine litter he inspected harbored potentially invasive species. In the even-more-isolated Antarctic, home to many species found nowhere else on earth, the influx of invasive species-hosting debris has been found to be more common than previously thought. In less remote regions, new species arrive frequently, and with few barriers.
And while natural modes of transportation – such as driftwood or even marine mammals like whales – also get unwanted species from point A to B, they tend to be less buoyant, less numerous and more constant in number throughout time than debris. Barnes also estimated that marine debris about doubles the opportunities for marine organisms to propagate at tropical latitudes and more than triples it at high latitudes.
Invasions of non-native species can be bad news for biodiversity – especially if the native species being pushed out are scarce in other parts of the world or are entirely unique to their ecosystems. Since much of the marine debris doesn’t break down quickly, and we keep putting more garbage into the ocean, these numbers are just going to keep increasing – unless we change our behavior.
The long-distance transport of exotic and unwanted colonizers is yet another reason to keep the oceans free of garbage. When you’re at the beach or river, take away everything you came with to ensure that garbage doesn’t reach our waterways in the first place. There’s no knowing how far garbage will travel once it takes to the sea – or who’s hitching a ride.