Development of a Planning Grant for a
National Initiative on Invasive Species
Timothy
Seastedt
1. The need.
Invasive plants, animals and pathogens present one
of today’s most important global environmental challenges, and they are a
leading cause of biodiversity loss and ecosystem change worldwide (Wilcove et al. 1998).
Estimates of the economic costs of invasive species to
the
Addressing the diversity of non-indigenous invasive
species in the
Biodiversity
loss, species change, and invasive species occupied two of the six themes of
the recent NRC report that has revitalized the NEON effort (NRC 2003). While we support the concept of separate
observatories or centers for biodiversity and invasive species themes, we
acknowledge a very strong overlap between the two topics (figure 1), and argue
that research and experiments focused on one topic will be relevant to the
second. These initiatives need to be developed such that each topic benefits
from the presence and activities of the other.
In particular, we envision large-scale, long-term experimental
manipulations and monitoring exercises that will
provide relevant information to both topics.
As
suggested by figure 1, invasive species can be influenced by other components
of global biogeochemical change, or the new species themselves can alter
ecosystem processes and
ecosystem
services. Either way, the biotic system
will be changed in ways that will have both direct and indirect effects on
sustainability issues, including species extinctions and ecosystem
services.
Figure 1. The relationship between
invasions, biodiversity, and other variables affecting biotic change.
2. LTER involvement in
Invasive Species Research.
The
LTER network was formed prior to the current scientific or societal concern on
invasive species. Nonetheless, the
'early' data sets collected in association with other research questions now
have substantial value in developing and testing current theories regarding
community invasibility and evaluation of invasive species threats. Three examples are Smith and Knapp's (1999,
2001) work on factors controlling invasibility in tallgrass prairie, the role of species
and functional characteristics in influencing invasibility
(Fargione et al. 2003), and Lauenroth
et al.'s (unpublished research) using plots established in the 1960s to
demonstrate the role of landscape legacies and soil biogeochemical effects on
the numbers and abundance of invasive species.
Within
the long-term data sets at various LTER sites are data on the transitory
responses following the 1930s chestnut blight, along with pre-
, ongoing and post- invasion data on insect outbreaks and other forest
pathogens.
The
LTER has the ability to make unique contributions to the study of invasive
species issues. First, many sites have
historical data sets that will allow for the analysis of invasion and spread of
nonindigenous species, and the relationship between invasions and species
losses and gains by native species.
Second, the LTER have extensive strengths in the relationship between
site biogeochemical processes and species composition and functioning. Sites also have extensive records of climate,
atmospheric nutrient deposition, and many sites have long-term manipulations
involving climate or nutrient manipulations. These experiments, originally
designed to test other questions, now are essential in determining the extent
to which invasive species are merely responding to environmental change, functioning
as ecological equivalents, or are particularly threatening in terms of their
abilities to alter ecosystem characteristics.
3. Planning Grant
Activities.
This
effort will undertake those activities viewed as essential to the development
of an invasive species research network.
We suggest that the planning activities attempt to achieve three
goals. First, we believe a complete
inventory of LTER historical data relevant to invasive species questions be developed. We
believe that all sites should compose the invasive species working group and be
involved in defining the importance and the dimensions of the science, and the
planning grant needs to obtain that input.
Finally, the planning grant should summarize this information and
develop what tentatively is viewed as an invasive species super-group. The group would then be charged with building
a hierarchical science organization with plans to involve sites in thematic,
science driven activities on invasive species that concurrently provide or exploit
crosscutting experiments and themes from other NEON and NEON-type initiatives.
Discussion
at the ASM indicated that there exist logical "sub discipline"
working groups within the invasive species super group. These groups likely include herbaceous ecosystems,
forested systems, aquatic systems, human-dominated systems, etc. While this division seems to be "habitat
selection", the major questions of these groups differ. For example, in
forests, the questions appear to revolve around change in the dominant plant
species driven by insect outbreaks and plant pathogens. In grasslands, the
focus is change in plant cover, while in aquatic systems the focus appears to
be on alteration of trophic dynamics. Sites dominated by human activities
conceptually see the ecological services of nonnative species very differently
than as "invasions". The thematic linkages will be determined by the
activities of the planning grant.
The
planning grant shall consist of the following activities:
I)
A data exploration activity be conducted to identify
LTER data sets useful in the analysis of biotic change. Data with any species lists can be evaluated
in terms of the origin of each species. We anticipate that this will include
such data sets as:
- Permanent plot and
monitoring data over space and time.
This dataset can be used to address the types of species invading
and being lost over the history of the monitoring at each LTER site, as
well as the temporal (e.g. correlations with climate) and spatial
variability in the pattern (i.e. across habitats within a site, across
sites, proximity to certain types of landuse). The remote sensing and GIS
capabilities at each site can also help build this dataset. Such plots are
viewed as useful for both plant and animal (herbivore, predator, or detritivore) invaders.
- Response to
experimental manipulations. Most LTER sites have large-scale, long-term
experimental manipulations of resources and/or disturbance as part of
their science focus. Examples include the addition of nitrogen and other
nutrients (water, phosphorus), changes in grazing and fire regimes, and
harvesting or removal of species (clear-cutting, specific species
removals). In the majority of these experiments, the response
of species (at one or several trophic levels) have been measured
throughout the course of the experiment. These measurements can be used to
examine whether environmental changes can facilitate the invasion of
certain types of non-native species and the loss of certain types of
native species.
As an example of the use of
these types of datasets, a synthesis of nitrogen addition experiments across
the LTER sites is already testing the whether increased nitrogen availability
can enhance invasion across the board, or if invasion in increased resources is
dependent on environmental context and/or functional type of the invader.
- Monitoring
records/experiments specifically focused on documenting the invasion
and/or loss of a species at a LTER site. These datasets would include
species/environment response (both target and non-target) due to an
invasive pest outbreak (e.g., hemlock woolly adelgid, gypsy moth) and
expansion of an invasive species (e.g. zebra mussels).
- Use of non-LTER
monitoring networks/databases. Other databases exist, such as county/state
inventories, National Park Service monitoring program, monitoring by the
Forest Service and Bureau of Land Management that could be used to
identify holes in the current LTER network coverage and more widespread
coverage in synthesis efforts. NEON, if it occurs, would also be a
resource.
II)
Qualitative site challenges. Each site will be asked to provide the following
general information documented, insofar as possible, with site information and
studies from their respective sites.
a. What controls invasibility of the ecosystem
b. What are the most invasive species (separately,
if possible, for plants, invertebrate herbivores, invertebrate
predators/parasitoids, vertebrate herbivores, vertebrate predators,
detritivores, etc), both in terms of abundance, ecological impact, and economic
impact?
c. What explains the dominance of the
"most invasive species"?
d. What invader(s) is/are the major threat to
biodiversity at your site?
e. What invader(s) is/are altering ecosystem
processes and ecosystem services and
how are these changes being accomplished?
f. What management activities are occurring at
your site in response to these species?
III)
Identification of integrative and innovative cross-site questions. We will hold
a series of meetings to further refine and identify the important questions in
invasion ecology, with a focus on issues that the LTER network can address.
Although this list needs much more debate and development, some critical ideas
that could be testable using standardized, experiments across LTER and non-LTER
sites (and/or satellites to LTER sites) include:
a. In diverse communities,
redundancy of functional types can buffer process rates in response to species
loss or gain.
b. In diverse landscapes with
multiple types of landuse, invasion and extinction processes are accelerated.
c. Unused resources are windows
of opportunity for species to invade that are capable of using those resources.
d. Species loss is accompanied
by species gain because communities are saturated.
e. Variation in propagule
pressure, disturbance regimes, and resource availability are the major
determinants of invader success.
f. Reversal of the drivers that
facilitated invasion will not exclude the invasive species because the invader
changes biogeochemical/structural of the system.
g. Species loss/gain in one
trophic level will impact other trophic levels. At other trophic levels, these
effects will be buffered in complex and connected systems and magnified in more
simple systems.
Initial
discussions concerning tests of these ideas focused on integrating two types of
experimental approaches: propagule addition/species removal and environmental
manipulations to enhance/reverse potential drivers. These experiments would be standardized
across habitats within each LTER and across LTER sites, accompanying
differences in invasion pressure, landuse history, community structure, and/or
resource availability. These experimental approaches would be combined with new
syntheses of existing data.
IV)
Organization and coordination. We would need to hire the right individual(s) to
conduct the data inventory/preliminary synthesis activity. If sites are to participate in the invasives
supergroup activity, they must provide information to section II and help with
section I. We also foresee the need to conduct a series of focused
workshops/meetings for the group during the planning phase to further define,
focus, and develop ideas such as given in section III.
V).
Species Extinctions.
A
research program focused specifically on mechanisms for species extirpations
would involve many dimensions not addressed here. We propose that, as part of
the planning grant a subcommittee working group within the biodiversity and
invasives programs be established to identify and clarify a research theme that
addresses this topic in a comprehensive manner. This group clearly would have
to work with other research teams outside the biodiversity/invasions group to
develop a robust research agenda. We believe the goal of this research agenda
would be to provide predictive capabilities of the relative risk of species
extirpations with respect to all components of global environmental change.
A
group commissioned by the Executive committee will be charged to summarize
these findings and incorporate this information into a major research
initiative.
References Cited
Council
for Agricultural Science and Technology. 2002. Invasive
National
Research Council, Committee on Grand Challenges in Environmental Sciences,
Oversight Commission for the Committee on Grand Challenges in Environmental
Sciences. 2001. Grand Challenges in Environmental Sciences.
National
Research Council, Committee on the Scientific Basis for Predicting the Invasive
Potential of Nonindigenous Plants and Plant Pests in
the
National
Research Council, Board of Life Sciences. 2003 NEON: Addressing the Nation's
Environmental Challenges.
Pimentel,
D., L. Rach, R. Zuniga, and D. Morrison. 2000.
Environmental and economic costs of nonindigenous
species in the
Riccardi, A. 2001. Facilitative interactions among aquatic invaders:
is an “invasional meltdown” occurring in the
Simberloff, D. and B. Von Holle. 1999. Positive interactions
of nonindigenous species: invasional
meltdown? Biological Invasions 1: 21-32.
Wilcove, D.S., D. Rothstein, J. Dubow,
A. Phillips, and E. Losos. 1998.
Quantifying threats to imperiled species in the