Ecosystems on our planet are, as we have learned over and over as a species that seems to live outside them, much more fragile than we've given them credit for. Sometimes it only takes the introduction of one species to upend the whole boat. This can happen naturally... say a flood or a windstorm blows an invader into a new biome that is not prepared for it... but it is usually humans that are responsible for bringing these invaders in. Sometimes it is by accident, and other times we do it to solve a problem that we, ourselves, have created; then going on to make it so much worse. Insects and viruses can be carried across oceans by boats, on livestock or even our clothing. Animals can be imported as pets and then let loose... or imported as a possible resource, and then found to be deeply destructive and impossible to control. Island ecosystems are deeply vulnerable, often having completely endemic, carefully balanced food chains and interspecies relationships. The introduction of a single new animal can, and has, completely upended that balance. Large-scale agriculture is also vulnerable to a single invader that it has no defense against. We can struggle to right these human-caused wrongs, but often find ourselves helpless in the face of an imbalance we have no way to fight. This is a list of the most destructive invasive plants, animals and diseases on Earth. Vote up the ones that you have experienced the impacts of, either directly or indirectly.
Origin: Brazil and Argentina
Originating in Argentina and Brazil, there are few that have never heard of the fire ant, one of the worst invasives in the world. In the US, it is thought that the first ant arrived in Mobile, Alabama via cargo ship somewhere between 1933 and 1945. In Australia it is believed to be closer to 2011. It has since caused billions of dollars in damage to the areas it now infests. The ants thrive in urban areas, so their presence may deter outdoor activities, but more damagingly, nests can be built under structures such as pavements and foundations, which may cause structural problems, or cause them to collapse. They also can damage equipment and infrastructure and impact business, land, and property values. As the workers are attracted to electricity, they can swarm electrical equipment and destroy it. In agriculture, they can damage crops, damage machinery, and threaten pastures. They are known to invade a wide variety of crops, and mounds built on farmland may prevent harvesting. They also pose a threat to animals and livestock, capable of inflicting serious injury or killing them, especially weak or sick animals. So far, the only ways of controlling these ants has been found to be baiting and pesticides. Due to its capability for damage, the ant has become one of the most studied insects on earth.
Origin: African/European Hybrid
The Africanized honey bee is a slightly unusual case, a bit of a Frankenstein's monster. It's a species cross-breed between aggressive Tanzanian bees and docile European honey bees. This was done as a way to try and increase honey production, however, the result was a very angry honey bee. That would have been the end of the story, but unfortunately in 1957, a beekeeper in charge of the hybrids accidentally released 26 Tanzanian queens in Sao Paolo, Brazil. These queens went out, found some european honeybees and multiplied. These hybrids are aggressive and hyper-territorial. They out-compete any native bees in the region they occupy. Africanized honeybee swarms have been known to invade regular honey bee hives, kill the European honey bee queen and install their own leader. They are less likely to store honey like the domesticated bees and they are quick to abandon a hive. The bees first infiltrated the U.S. in 1990 and have since spread to the southern parts of many states, including California, Nevada, Utah, Arizona, New Mexico, Texas, Oklahoma, Louisiana, Arkansas and Florida. Despite what fun TV movies of the week might make you think, their sting is no more toxic than any normal honey bee, however, because of their intense aggression, they have been known to swarm easily and sting many times, making them a threat to humans as well as honey production.
Origin: Northern Asia
This small, striped day-biter has been in the news in recent years in California, having newly arrived to join the phalanx of ultra-annoying mosquito species that already live there. Previous to California, it was first found in the US in 1985 in Texas. Since that time they have been spreading rapidly and unabated across the country. They prefer warm weather, so they have been identified in every county in Georgia, Florida, South Carolina and Tennessee, as well as many counties in surrounding states. They breed in small puddles of standing water near human habitation, in diverse places, varying from cemetery vases to junk piles. Like other invasive species, the Asian tiger has out-competed native mosquitoes, such as Aedes aegypti, the yellow fever mosquito, but that's not necessarily good. The tiger mosquito can spread diseases too, such as West Nile, dengue fever or Eastern equine encephalitis. In fact, its habit of staying close to where people live and biting multiple hosts in the daytime, make it an even more efficient vector for some diseases. Stay safe by following standard anti-mosquito protocols; including removing any standing water source from near your house if possible, no matter how small.
Going by several not-so-flattering nicknames, Kudzu is well known to areas that is is not native to. It's hard to miss, as it covers everything. The Kudzu vine is native to Japan, but arrived in the US in 1876 when it was featured at an expo as a hardy, fast growing vine that could fight soil erosion. Well. They weren't wrong about that part. Also known as the 'mile a minute' vine and the 'the vine that ate the south', Kudzu has been spreading across the country at 150,000 acres a year. In the right conditions, a length of vine can grow a foot in a single DAY. The vines themselves grow up to 100ft long and the plant can smother trees, houses, power lines and whatever else that can't move out of the way. It is drought and frost tolerant and practically unstoppable. Nothing can compete with it, and thus, it wins. This invasive easily sits in the top 10 of the worst case scenarios that happen when an organism has no natural barriers built into its ecosystem.