A Silver Lining for Invasive Species
Burmese pythons are one of the well-known, sensationalized invasive species in the U.S.—some might even call them notorious. While the story of giant snakes gobbling up anything that moves in the Florida Everglades offers a dramatic cautionary tale about invasive species, there’s a deeper drama to share. It’s the inspiring story of the determination and ingenuity of invasive species scientists who are devoted to understanding and solving this issue.
Burmese pythons are easy for most people to villainize because they are creepy crawlies that, under certain conditions, could be dangerous. It is easy to imagine the impacts a giant snake could have on a unique wetland ecosystem like the Everglades, which was already struggling because of the activities of people by the time pythons showed up in the late 20th century.
The USGS is a leader in invasive species science, so when it became clear that the Everglades had a python problem, USGS scientists were brought in to help develop methods for detecting, understanding and controlling them. I was lucky to join that team relatively early in their involvement.
Early on, I was optimistic about the ability of science to solve the challenge of invasive species.
The first python-related research study I worked on was testing whether pythons could be trapped. The answer was technically yes, but the trapping methods used in the study weren’t going to work as a control tool for many reasons, including that only a handful of pythons were trapped over the span of several years.
We moved on to trying other ways to understand these giant snakes and control their population. Meanwhile, more and more evidence piled up showing the devastating impact that Burmese pythons were having on the Everglades ecosystem.
It turns out, Burmese pythons are incredibly well adapted to living in the Everglades. They are semi-aquatic so the seasonal rise and fall of water levels in the ecosystem hardly matters to them. If you’ve never seen one in the wild, they blend in better than you can imagine, and they can hold very still for long periods of time.
Once, while I was radio-tracking a python in one-foot-deep water with a coworker, we ended up standing practically on top of it without seeing it, even though we knew it was close by. It was a 10-foot-long snake.
Over the years I spent working in invasive species science, brilliant and determined scientists tried many techniques with the goal to curb the python problem. But none of the traditional methods for animal control that they tried on Burmese pythons—trapping, hunting, scent detecting dogs—seemed to be an easy fix to completely remove pythons from the complex Everglades ecosystem.
People kept finding pythons, and the pythons kept spreading.
Just as I questioned my own hope for a python-free Everglades, a paradigm shift in invasive species management was underway. The newer paradigm recognizes that invasive species are a type of problem with no easy solution—what has been called a “wicked” problem. I’ll admit, considering the enormity of the challenge, giving up was a temptation.
But no matter how tough it is to solve the problem of invasive species, we can’t deny that they are causing increasingly negative effects in the places they’ve invaded, including by wreaking havoc in communities.
Their presence also costs a lot of money. From 1960-2017, scientists estimated invasive species to have cost the U.S. over $1.21 trillion. Annual costs are increasing and since the 2010s, invasive species are estimated to have cost the North American economy at least $26 billion per year. And those costs are likely extremely underestimated.
Over time, USGS scientists and partners were steadfast in pursuing the answers to basic questions about Burmese python ecology in Florida, and they grew bolder in thinking creatively about how to find and remove them.
A new USGS study is exploring the use of python reproductive pheromones as a lure, which, if effective, could improve removal methods like trapping. Additional pioneering USGS research tests advanced DNA technologies to better to detect python presence and catalog what pythons are eating by sampling their poop.
Invasive species scientists, like my former colleagues, provide the invasive species silver lining. It is their refusal to quit and innovation that inspires hope.
Infamous invasives from dreissenid mussels to invasive carp species pose their own “wicked” problems in ecosystems around the U.S. Despite the overwhelming challenge, USGS invasive species scientists are not throwing in the towel on these issues. They are thinking creatively and embracing new technologies to help minimize the spread and negative consequences of invasive species.
The four species of invasive carp plaguing U.S. waterways have been a focus of USGS science for decades. But savvy scientists recognized they could use the carp’s sensitivity to noise against them.
The USGS is a leader in developing carp deterrents and, along with partners, is exploring how to use sound to change carp behavior and keep them away from specific areas, like an underwater megaphone broadcasting “Go away!”
These underwater acoustic deterrent systems, or uADSs, are promising because, so far, they don’t appear to disturb native species. The USGS is leading a project to test one such uADS in the Mississippi River.
A similar, more whimsical-sounding, technique that the USGS is working with partners to test is the use of bubble fences. These bioacoustic fish fences combine bubbles, sound and light to prevent the spread of invasive carp into new waterways. Personally, I think I’d be drawn to bubbles, and luckily, native fish aren’t deterred by the bubbles or sounds either.
Another inventive invasive carp control tool that USGS scientists are developing is carbon dioxide. They are testing the potential of carbon dioxide to act as a deterrent to invasive carp movement and as a toxicant to help reduce carp populations.
Although it is low tech, carbon dioxide is such a promising a control tool for aquatic invasive species that USGS scientists are testing it on other invasive species as well.
One example is the infamous zebra mussel. USGS scientists are testing whether carbon dioxide can be used to prevent zebra mussel larvae from settling on surfaces.
Along with quagga mussels—the other dreissenid mussel that has invaded lakes and rivers of the U.S.— these infamous mollusks have dominated the invasive species headlines for years. Dreissenid mussels are prolific filter feeders that disrupt native ecosystems and quickly grow into biological blankets that completely cover underwater surfaces and clog vital infrastructure, causing steep economic impacts.
Being able to prevent dreissenid mussels from growing is important.
There are existing control tools that are effective at managing dreissenid mussels. However, some may pose a risk to native species or may not be applicable over wide areas.
USGS scientists are investigating whether a molecular technology called RNA-induced gene silencing, or RNAi, could be used to reduce dreissenid mussel populations. Although it sounds very futuristic, RNAi has been around since the 1990s. Notably, however, USGS scientists are the first to test RNAi in the control of an invasive species.
While many of these approaches are still experimental, there are proven examples where scientists’ innovation and reluctance to quit have turned the tide on biological invasions.
Take sea lamprey, for example. These toothy terrors invaded the Great Lakes, and by the 1940s were decimating native fish populations and harming the economies of lakeside communities.
Fortunately, invasive species scientists developed two methods of sea lamprey control that helped to reduce the population immensely, a selective pesticide that kills sea lamprey larvae and barriers that prevent sea lamprey migration.
Climate change may lessen the effectiveness of successful lamprey control techniques, but inventive USGS scientists and partners have already been developing supplemental methods of sea lamprey control using new technologies.
Two cutting-edge examples include exploiting male sea lamprey reproductive pheromones to lure egg-carrying females into traps before they can successfully spawn and a picky fish passageway that uses images to identify fish and prevent sea lamprey from passing through.
USGS invasive species scientists don’t just focus on control tools. It might seem trivial, but a basic need for the management of invasive species is to simply know where they are present. As a leader in mapping and data management, the USGS has an important role in addressing this need.
A shining example of this leadership is a database that is possibly the crown jewel of the USGS invasive species program. In the late 1990s, USGS scientists developed the Nonindigenous Aquatic Species Database to report and map aquatic invasive species. Today, it is considered the “gold standard” and is used by many agencies in the U.S. and even some in Canada and Mexico, to track aquatic invasive species.
While it’s true that we don’t currently have a cure-all method to safely eradicate or nullify the worst invasive species from the areas they have invaded, we do have dedicated invasive species scientists. Technology is always advancing and USGS scientists will continue to lead the field in developing new ways of finding and managing invasive species.
Their ingenuity and commitment have renewed my own hope for an Everglades no longer constricted by Burmese pythons. They’ve also restored my optimism that science can find a solution for the landscapes and communities across the country dealing with similar invasive species-created wicked problems.
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