Invasive feral pigs present a problem for the Hawaiian Islands and their native ecosystems.
Feral pigs are one of the most widespread and damaging invasive species throughout the world. On the Hawaiian Islands, invasive feral pigs are a common sight and are now extending their reach from wild regions into urban areas.
Invasive feral pigs harm the natural island ecosystem by digging up native plants and creating niche spaces for non-native species. As the species search for earthworms and other food, they remove healthy native vegetation and disturb the ground. Such disturbances inhibit native species’ growth and can allow non-native species to settle where they may not have before. Pamela Scheffler, a researcher studying invasive feral pigs in Hawaii explained:
Feral pigs also eat or otherwise destroy native vegetation; cause changes in soil; act as dispersal agents and create habitat for exotic plants.
A study published last year in the Royal Society Open Science evaluated the genetic makeup of Hawaii’s invasive feral pigs and determined that they have genes both from Polynesian pigs and Eurasian boars. Although the Polynesian pigs were introduced first, the introduction of the Eurasian boar is believed to have caused a more extensive impact on the island due to their aggression. The study noted:
It was probably not until the twentieth century, with the introduction of new sources of protein such as earthworms and invasive fleshy-fruited plants that pigs were able to thrive in the forests, thus becoming a significant problem to the native flora and fauna.
Past research projects in Hawaii have shown a direct negative impact of the invasive feral pigs on the abundance of native plants as well as the effect they have on the abundance of mosquitoes, which use stagnant water as breeding grounds. Scheffler commented:
They also create mosquito breeding habitat by knocking over and hollowing out troughs in native tree ferns and making rain-filled wallows.
Increases in mosquito habitat create a host of problems for native birds and humans. Avian Malaria is a disease deadly to native birds and is threatening already-endangered native species.
The impact of invasive feral pigs on Hawaii’s native ecosystem is extensive. This research only shows the beginning of the changes these invasive species can have on the islands. Understanding these impacts can inform the management of invasive feral pigs and the protection of native flora and fauna.
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- BBC’s The Inquiry Features Island Conservation CEO, Karen Poiani - January 14, 2019