Understanding Plant Invasions in National Wildlife Refuges

NCEAS undergraduate research projectNational Center for Ecological Analysis and Synthesis

Background and context:• Invasive species are a major conservation

issue in protected areas because they do not respect reserve boundaries

• Invasive plants can reduce or eliminate native plants from protected areas

• Invasive plants can alter habits (e.g. wetlands) in ways that adversely affect wildlife and species diversity

National Wildlife Refuges:

• Over 500 in the U.S. and associated territories• Often established to protect a specific animal

species or habitats• Refuges appear to vary widely in terms of

invasive plant impacts – some report very few problems, others consider invasives a major issue

Scientific questions:• What factors tend to promote or prevent invasive plants

from establishing? Is invasion a function of refuge size? Habitat heterogeneity? The pool of exotics in the area?

• Does a high diversity of native plants help resist the spread of invasives?

• Are the factors that determine the number of exotic plants in a refuge the same as the factors that determine the number of aggressive invaders?

• Are the models that best explain the richness of invasives consistent from one region to the next?

Project outline:• ~450 refuges divided among eight classes• Each student will typically be assigned 5-10

refuges within his/her own region• Each refuge will be assigned to 2-3 students to

ensure accuracy• Your job is to compile all the necessary data

for your assigned refuges

Project Website: https://groups.nceas.ucsb.edu/sun

•Site contains most everything you’ll need for the project (data sheets, protocols, links, etc..)•Site is searchable, so if you can’t find what you need, type it into the search box•Use the discussion board under the “help” tab to ask questions

Data needed for each refuge (partial list) (predictor variables)• Area of refuge, elevational range of refuge• Number and distribution of distinct habitats within the

refuge (habitat heterogeneity)• Number of native plant species in the refuge• Number of exotic plants in the county surrounding the

refuge (exotic species pool) (response variables)• Number of exotic plant species in a refuge• Number of “problem invasives” in the refuge

Where will the data come from?

1) National Wildlife Refuge Invasive Species survey.

• A websurvey of refuge managers carried out in 2002

• Contains data on refuge area, elevation, habitat cover, and lists of “problem invasives”

• Some refuges have more complete information than others

Where will the data come from (cont.)?

2) Contacts (usually e-mail) with refuge managers or biologists

• You’ll use this approach to fill in gaps in Invasive Species Survey data

• Also to get plant species lists for as many of the refuges as possible

Where will the data come from (cont.)?

3) Refuge websites – used to get lists of plant species for the refuges (available on maybe 20% of the sites)

4) Biota of North America – used to get lists of exotic plants in the area near each refuge

What happens to the data?• Data entered into a spreadsheet for your class• Your class will analyze the dataset for your

own region to determine the factors that best explain the number of exotics/invasives in each refuge

• Your data and analysis will then get uploaded to the group site for analysis

Limitations and challenges:• Data are patchy and hard to come by (particularly species

lists)• Some data are of poor quality – species lists are often

compiled by one or two people, they generally haven’t been validated

• Classifying plants as exotic is usually (though not always) straightforward. However, the list of “problem invasives” is based on subjective impressions of refuge managers

• Hope is that large volumes of data can compensate for these issues with data quality

A few things to bear in mind:

• This is real science. We have no idea what we’ll find out. That’s why we’re doing the project

• Unforeseen complications are part of science. Be patient and we’ll do our best to work through whatever issues arise.

• We don’t expect you to be an expert on invasive species or data analysis – if you have a question, always ask

List of most commonly reported invasive plants in the Invasive Species Survey

Typical region – note 82% response rate, and that only about half of the refuges (25/49) report non-native plant information

NWR managers tend to rate invasive plants as a problem or significant problem

But most information, comes from anecdotal observations or “best guesses”