October 22, 2015

Study’s findings important for planet’s biodiversity

by Tim Crosby

CARBONDALE, Ill. – The United States has always been known as a nation of immigrants and research involving a Southern Illinois University Carbondale plant biologist says the same is true for plants. 

In fact, it’s true for the entire North American continent, where such alien plants have become quite at home and in many cases, “naturalized.” 

Daniel Nickrent, professor emeritus in the Department of Plant Biology at SIU, participated in a recently published study that includes a first-ever comprehensive analysis of global accumulation and exchange of alien plant species between continents. The results of the study, published in the leading science journal “Nature,” relied upon a massive and unique global database containing information on naturalized alien plant species in 481 mainland and 362 island regions. 

The study is based on an enormous database called GloNAF (Global Naturalized Alien Flora) assembled by the lead author from data provided by researchers around the world. The results for the first time quantify the extent of plant naturalization worldwide, as well as the “flows” of such alien species, showing where they came from and where they are going. It also underscores the urgent need for global, coordinated efforts to control, manage and understand the spread of alien species, the authors said. 

The findings hold serious implications for the planet’s biodiversity. Although the naturalized plants are sometimes harmless, in many cases they can become “invasive,” aggressively asserting themselves into the ecosystem and significantly altering the environment by choking out native plants and forcing species to adapt or perish. 

Nickrent, who was one of about 40 international co-investigators on the project, said the survey is a major step forward in understanding and dealing with the threat of invasive species. 

“To me, controlling invasive species is the No. 1 problem worldwide in terms of natural ecosystems,” said Nickrent, who along with two colleagues provided a large amount of data about Philippine flora. “We even have (invasive species) here on campus at SIU.” 

Alien plants often are introduced into new areas by humans, who might do so by planting crops, bringing along ornamental plants, or simply by accident. The study, which involved 33 research institutions, found that 13,168 plant species or nearly 4 percent of the global total have become naturalized because of human activity. 

The study showed that North America has had nearly 6,000 non-native naturalized species introduced since Europeans arrived in the 15th Century. Europe, meanwhile, has more than 4,000 alien plant species. 

Nickrent, along with Pieter Pelser and Julie Barcelona, contributed data originally assembled by Leonardo Co, a famous scientist and expert on the plants of the Philippines. The trio took it upon themselves to watch over, maintain and expand on the data after Co was killed in 2010. 

“Leonard was like a walking encyclopedia of Philippine flora and we felt a need to get his stuff out there and not let it die,” Nickrent said. “So we were able to get his hard drives that contained his photos and other records, put them together and make them available online.” 

It was essentially this vast record – more than 10,000 lines of database entries -- that Nickrent and his colleagues provided to the overall effort. Looking at the big picture, as this study does, the information provided by Nickrent and his colleagues showed the Philippines also are among the most impacted by alien plant migrations. 

“North America got an unduly bad share of naturalized and invasive plant species when compared to most of the rest of the world. But the data show the Philippines are also red hot with this activity,” Nickrent said. 

The flora on islands often are strongly impacted by invasive species. Nickrent said this may be because of geographic isolation. 

“Because islands are isolated the native plants there don’t have a lot of competitors. So they’re kind of the weaklings in ecological sense,” he said. “Then when you bring in these aggressive species from elsewhere that have been competing for their whole existence, it’s like dropping a bomb on them. 

“We’re losing the native local flora in many cases, and the more this happens the more chance those species can go extinct,” Nickrent said. “We don’t know everything about them, in terms of medicines they might provide or the impact on ecosystems or even their aesthetics. I think it’s our duty to preserve what’s here for future generations.” 

A scientist like Nickrent is always alert for new developments in this area. Sitting at a stoplight on Illinois 13 recently, he looked out his window and spied a grass that looked different from any others he had seen in the area. He made a specimen and did some research and found out it was a species that is native to the southwestern United States that is making its way east.  

Nickrent also is concerned about another invasive grass species, Microstegium vimineum, a stalky, grass with leaves also known as Japanese stiltgrass, which has found a niche in places on the SIU campus. 

“It’s another example of a terribly invasive plant,” Nickrent said. “The trouble is we never know which one of these is going to be the next Autumn Olive Tree,” he said, referring to a fast-growing, invasive species that is doing damage in many places around Southern Illinois.