Invasive alien species universal challenge

The World Parks Congress raised many issues and our reporter Ishbel Cullen has summarised one discussion which strikes a chord across this planet: the impact of invasive species on local species and biodiversity.

A love of the plants and animals of this world unites everyone attending the World Parks Congress. However, this love does not extend to species that have spread beyond their original geographic location to foreign destinations, where they behave recklessly and create havoc for the locals. From raccoons in Poland, eucalypts in California and cats just about everywhere, invasive species are a major threat to biodiversity around the world.

At the ‘invasive alien species’ session, we first heard from the General Manager at the Corbett Tiger Reserve in India, who started his presentation by saying, “if you want to see what lantana can do to nature, you have to come to Corbett Tiger Reserve.” Lantana is an invasive plant species well known to our own country and classified as one of the world’s ten worst weeds. The staff at Corbett Tiger Reserve are on the offensive and have developed a new tactic for combating lantana called the ‘cut-root method’. This involves cutting the taproot just below the coppicing level and then placing the shrub upside down, so it can’t re-establish. This technique avoids disturbing the soil and is proving successful as part of a wider lantana strategy. However, there are large educational issues remaining, with lantana still being grown as an ornamental at Presidential House in Delhi. [See this map for the spread of lantana in Australia.]

The next speaker was passionate about a slightly broader theme, islands and invasive species. With 70% of known extinctions, islands are high-risk areas for losing species, however, islands also present unique opportunities for conservation. The representative from Island Conservation stressed the strategic importance of targeted invasive species eradication programs on islands. To date, there have been more than 1300 invasive species eradication attempts globally and 907 of them have been successful. The strength of biosecurity regimes often determines eradication outcomes, meaning island military bases often have the best results.

Many of the successful eradication programs have lead to dramatic and immediate changes. On Palmyra Atoll in the northern Pacific Ocean rodents were eradicated in 2011, resulting in a large increase in new native tree seedlings because the rodents aren’t eating all the native seeds anymore. On San Nicola in the Channel Islands of California, cats were eradicated in 2010 and now the local Island Night Lizard has achieved a rare feat, being removed from the threatened species list because of population recovery.

With the climate changing, island conservation efforts are of particular importance. With many islands facing complete inundation, available habitat will be reduced and remaining higher islands could serve as ‘biodiversity arks.’

The next speaker in the session was from Brazil and discussed the difficulty of invasive native species, a topic that resonated with many in the room. In Brazil, Tamarin monkeys are both endangered in some areas and invasive in other areas. This raises difficult questions for how to manage the species within one jurisdiction, under the same threatened species laws, when having to kill a species in one area and protect it in another area of the same country.

The diversity of speakers and members of the audience demonstrated that managing invasive species is truly a universal challenge. When ecosystems are disturbed and the will of species to live, compete and reproduce goes unchecked, this force of life becomes a force of destruction. The real question: how to manage the most invasive species of all?