Sci/Tech Presents: Invasion Biology
The islands of Hawaii have been ravaged by invasive species ever since the second wave of Polynesians landed on their shores in the eleventh century, deciding to bring various plant and animal species along with them. Hawaii was a vulnerable environment, with its native species having never faced competition and predation from large mammals. The native flora, having never had to defend themselves against grazing animals, never developed the spines, toxins, or thorns necessary to fend off the hungry herbivores that suddenly populated the islands. The native birds, also completely unprepared for the various new inhabitants, were left devastated by the newcomers.
The Hawaii of today is a completely different place than the Hawaii of old, with hundreds of new invasive species, bringing with them many environmental and ecological problems that threaten the health of the islands.
Invasive plant species are incredibly detrimental to the ecology of the Hawaiian Islands and have taken over many areas of native forest. Most of the invasive plant species on the islands were introduced originally as garden plants, later escaping and thriving in the warm climate. One of the more devastating of the invasive plants on the islands is miconia (Miconia calvescens) otherwise known to locals as “green cancer” or the “purple plague,” after the unique purple colour on the underside of its leaves. It has grown to incredible numbers thanks to its ability to bear fruit two to three times a year, producing three million seeds per plant each fruiting period. Miconia can grow up to fifteen metres tall, taking much of the nutrients, water, and sunlight that the shorter native plants require. The most detrimental aspect of miconia is its shallow root system. Miconia's proliferation has led to many devastating landslides in areas all over the islands as the deeper-rooted natives, which help combat erosion, are outcompeted and die off.
Another incredibly detrimental invasive plant is Banana Poka (Passiflora mollissima), which, like miconia, was originally brought to the islands as a garden plant. The word poka in Hawaiian translates to the verb “to climb,” which is how Banana Poka infests Hawaiian forests, choking out any native species in its path to the point of 100 per cent coverage in some of its most prominent areas. It’s a relative of passion fruit and bears similarly sweet fruit that animals can’t resist, helping to further its spread by transporting its seeds.
Many animals have been brought to the islands over the years as farm animals or house pets. These animals eventually escape, breed, and form wild populations, referred to as feral. Everything from pigs to house cats have established populations on the islands, wreaking havoc on nearly every native species. Feral pigs quickly destroy the forest floor, trampling every low-lying plant, turning the ground into sticky mud, and ultimately killing the forest from the ground up. They dig wallows in the mud, creating stagnant pools of water -- perfect breeding grounds for disease-carrying mosquitoes. Feral cats pluck unsuspecting native birds from their perches as an easy meal, decimating their populations and driving many to near extinction. Most of the feral cats on the Hawaiian islands are full of diseases; many are sick with a feline form of leukemia and some carry toxoplasmosis, a parasite that could have detrimental effects to humans with weakened immune systems.
The Hawaiian Islands have been thrown into chaos from the overwhelming numbers of invasive species landing on its shores. Hopefully all the damages caused by these species can be mended or at least slowed in the future before all original ecological and environmental signs of the Hawaiian Islands are erased forever.
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