Humans have spent most of our time on Earth bending and twisting nature to fit our needs and wants. About 12000 year ago, we figured out that if we purposefully grow a few plants in large amounts, then we could survive the seasons in one place. We also learned that if we hold on to a few of the more docile animals, then we could form our own herds of food that go where we go, or better yet, stay where we stay. We evolved from our hunter-gatherer ancestors into a people that can cultivate our own sustenance, and we never looked back. Our new skill made us quite adept at sustaining plant and animal species in places where they didn’t quite belong, but we haven’t done very well at addressing the consequences of the spread of invasive species – organisms that do much more harm than good in new environments.
Invasive species are brought into new areas in a number of ways. Some animal species, such as the Burmese python of Florida or the lionfish of the Caribbean, are imported as pets and released into the wild when their owners tire of them (US Department of Agriculture). Plants such as the Chinese tallow, an ornamental plant introduced to the US in the 1700s, still outcompetes some native plants in the south today (USDA). Other species such as the red imported fire ant (introduced to the US via a cargo ship), are brought into new areas by accident (USDA).
For a while, our solution to this problem was to fight nature with nature. With our vast knowledge of the way world works, we paired our pests with likely predators from all over the world. The cane toads introduced to Australia to protect sugarcane saved the crops, depleted the food of Australian native species, and killed anything that made the mistake of eating it. The weevils introduced to North America to control the bothersome Musk and Canadian thistle didn’t just eat thistle. The list goes on. Obviously there were some details we missed when we attempted to pit nature against itself.
It’s time that we start looking at the way that these species spread. Sometimes these organisms do not occur in areas that they statistically appear. It makes us wonder what it is about one habitat that can sustain an invasive species that is so different from another similar habitat, or what is it about the invasive population that is so different from the original population. Wayne Dawson of the University of Konstanz said that “novel plants in novel environments means novel interactions, which sets the stage for evolution to continue in a way that would be different if species remained geographically separated on their own continents of origin.” This can be true of any species Narrowing down where exactly a species may spread next may help us understand what makes their invasion of new habitats so successful.
Kumar P. Mainali and a team of scientists from the University of Maryland took the first step to do just that. Using the weed, Parthenium hysterophorus, as a model species, Mainali and his team compared four statistical models for species distribution to each other in order to determine which would be the best to predict the spread an invasive species, and to improve upon each statistical model. P. hysterophorus is a weed with a great global presence. It has spread from its origins in the tropics of the Americas to Africa, Australia, and Asia. Perhaps with the improvements of these models we won’t be blindsided by the results we desired to see. Instead, we will be given a well-rounded idea of the species we have transferred from one place to another. The information provided by these improved models should also allow us to develop a management plan as we track its potential spread. The use of these models could be a fantastic way to determine whether or not humans are truly ready to play with nature.
Mainali, K. P., Warren, D. L., Dhileepan, K., McConnachie, A., Strathie, L., Hassan, G., Karki, D., Shrestha, B. B. and Parmesan, C. (2015), Projecting future expansion of invasive species: Comparing and improving methodologies for species distribution modeling. Glob Change Biol. Accepted Author Manuscript. doi:10.1111/gcb.13038
Wayne Dawson, quote from Sweet smelling water hyacinth is trouble by Klaus Esterluss. DW.
United States Department of Agriculture. National Invasive Species Information Center (NISIC): Gateway to invasive species information; covering Federal, State, local, and international sources.