For decades, Florida communities have battled invasive plants on land and water. These plants disrupt native ecosystems and livelihoods, and more arrive each year.

Now a new study from the University of Florida and The Nature Conservancy shows that nearly $45 million in state and federal funding per year is spent in Florida to gain the upper hand on invasive plants in natural areas and waters, and that success depends on how well control efforts are funded.

Florida consistently ranks among the top three states most affected by invasive plants, said S. Luke Flory, associate professor of ecology with the UF Institute of Food and Agricultural Sciences and one of the study’s authors.

“Most plants have what we call ‘natural enemies,’ which are pests, diseases or predators that keep plant population at stable levels. When a plant is introduced into a new area, the natural enemies that used to keep them in check in their native habitat may not be present in that new area. Without any natural enemies to stop them, these new plants may dominate, negatively impacting existing plants, wildlife and the people who use those areas,” Flory said.

For instance, aquatic plants such as hydrilla and water hyacinth clog waterways and drainage canals. Cogongrass increases fire risk and decreases pasture for cattle. Air potato can engulf natural areas with its fast-growing vines, and Brazilian peppertree can alter habitat and diminish recreational value.

Nearly 1,500 non-native plant species have established in Florida. Only a small fraction of these species become invasive, but those that do present a significant threat to the state’s $50 billion natural resource-based sectors, the study’s authors say.

However, the study shows that funding initiatives to counter plant invasions have been an effective and efficient investment.

“Our findings demonstrate the need for continued and sustained funding to efficiently address and manage the growing problem of invasions,” said Kristina Serbesoff-King, a scientist with The Nature Conservancy and one of the study’s co-authors.

“Florida has a relatively high level of commitment to invasive management – but it is unclear if current spending is sufficient to prevent the establishment of new non-native species or dampen the spread of current invaders,” Serbesoff-King said. “Consistent management with sufficient and sustained funding is more effective than only increasing spending when invasive plant populations become highly problematic.”

The study draws from six years (2009 to 2014) of state and federal expenditures on control of invasive plant species in Florida conservation areas. Researchers looked at where money was spent across the state with respect to known plant invasions.

Their results suggest that in Florida, funding has gone toward controlling the most problematic invasive plant species where they are most abundant and of greatest concern. The study also found that greater management expenditures led to less area invaded for the costliest invasive species, hydrilla.

Florida has many examples of successful control of invasive plants, including melaleuca and others. But, as with nearly all invasive plants, the extent of control is directly determined by the amount of resources dedicated to it, Flory said.

In the long term, invasive species decrease biodiversity—the variety of plants and animals in an area. A recent UN global biodiversity assessment identified invasive species as a key driver of the decline of biodiversity and ecosystem services globally.

Future research on invasive plants in Florida will need to identify emerging problem species, locate them when they are small, test control methods and determine when and where management is most effective, the study’s authors said.

In addition to Flory and Serbesoff-King, the study’s authors include lead author and UF /IFAS biological scientist Drew Hiatt; Deah Lieurance, assistant Extension scientist and coordinator for the UF/IFAS Assessment of Non-native Plants in Florida’s Natural Areas; and UF biology professor and Environmental Defense Fund lead senior scientist Doria Gordon.

The study was published in the journal Conservation Science and Practice.

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