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Climate Change: Improving Restoration to Meet Shifting Plant Communities

Kate Gazzo, M.S.

As an ecologist understanding how changing climates affect restoration can be essential to a project’s success. Questions which arise include; how likely is a restored wetland to remain wet in an increasingly Mediterranean climate, and what is the success of restoring a tidal marsh along a coast that is predicted to be underwater in 100 years? Considering millions of dollars are often spent on restoration projects, the projected biophysical conditions of a project region should be considered to secure the long-term success of a project and protect the financial investment that has been made to restore a site.

Results produced from mapping biophysical shifts within the U.S. show that half of ecosystems will be unable to maintain historical conditions, as a result of increased greenhouse gas emissions and will experience changes in soil, temperature, and/or precipitation (Figure 1). In many areas of the U.S., predominantly in the south and much of California, dry areas are predicted to become increasingly arid, while wet areas such as the Pacific Northwest will receive increased precipitation.

Mapping Biophysical Shifts within the U.S.

Figure 1. Map of 500 ecoregions within the U.S. responding to a rapid greenhouse gas emissions scenario (735-1080 ppm CO2) and displaying relative changes in temperature, soil, and precipitation. Colors indicate which factors have the most dominance. Image source: Saxon et al. 2005.

How is climate change affecting vegetation communities?
One of the biggest restoration concerns stemming from climate change is the long-term stability of vegetation communities. While specific effects at any scale (community, population, or species) are hard to predict due to plant adaptations and migration rates, some consistent predictions exist. These include: poleward shifts, upslope elevation shifts, and replacement of native species with invasives which are tied to long term changes in temperature and precipitation patterns (Walther et al. 2002).

Poleward Shifts

Vegetation communities will experience latitudinal or, poleward shifts, as a response to long term changes in temperature and precipitation. Examples of poleward shifts include the appearance of shrubs in prior shrub-free regions of Alaska and predicted northward advancement of eastern tree species by as much as 250 km- a change that would lead to these species no longer having ranges within the U.S. (Iverson and Prasad 1998).

Elevation Shifts

Elevation shifts are another effect resulting largely from changes in temperatures and also precipitation patterns. These shifts are oftentimes upslope and occur as plant communities shift into more suitable temperature ranges. Unfortunately, for vegetation communities distributed along ridges and mountaintops which are nearing their temperature and precipitation thresholds, there is no suitable habitat for these communities to shift to. Vegetation communities that are particularly at risk are alpine/subalpine and conifer forests. Within California, warmer temperatures are predicted to have a significant effect on the percentage of alpine/subalpine (-77%) and conifer (-51%) forests as these communities are pushed out of current habitat ranges (Figure 2).

Temperature modeling of CA's vegetation communities

Figure 2. Temperature modeling of California’s vegetation communities under historical conditions (left) coupled with a 4°C temperature increase (right) (GFDL-A2). Note the significant decline in alpine/subalpine and conifer forests.         Image source: Lenihan, et al. 2008

Increases in Invasive Species

In addition to changes in plant community distributions, plant community compositions will also change. As the ideal habitat range for native species shifts, we will likely see competitively dominant invasive species replace native species. For example, in Arizona, prolonged drought over the past twenty years has already been attributed to widespread pinyon pine mortality and invasion by juniper (a native species dominant in lower elevations) (Mueller et al. 2005).

Integrating Climate Change into Planning and Restoration

Pinon piness killed by beetles

Pinyon pine mortality and invasion of juniper in the southwest.          Image source: National Park Service 2015.

Because the success of restoration projects largely depends on the survivorship of plant communities, climate change planning is being increasingly incorporated into planning and design of projects. Effective planning requires additional consideration of the future biophysical conditions, not just historical and current conditions when forming restoration goals. Future climate scenarios are derived from mathematical representations of the interactions between the earth, ocean, and the atmosphere which calculate changes in precipitation, sea level rise, temperature, and other variables over time.

overview [Converted]

A graphic representation of Great Ecology’s coastal resiliency modeling for the township of Stony Point, New York.

The Coastal Vulnerability Index (CVI) is one example of a model which maps coastal areas most at risk to Sea Level Rise (SLR). This particular model was used by Great Ecology to assess SLR impacts at three locations within the New York-New Jersey Harbor Estuary. Results from modeling were then used to form recommendations to build resiliency at each location.

In addition to modeling, there are a number of other techniques that restoration managers can implement to ensure the long term success of projects, these include:

      1. Creating a record of the biological, physical and chemical changes within site conditions over time. Trajectories can be formed based upon monitoring data over the course of time to plot how site conditions are changing. Some examples of long term monitoring could include tracking changes in plant community composition, soil chemistry, and salinity intrusion.What biological, physical or chemical condition will shift and by how much is unknown. Adaptive management can be used to address small changes in site conditions, however, it is much more cost-effective to incorporate resiliency and sustainability into plans during design than to re-construct site conditions after site establishment and succession has begun.
      2. Therefore, creating a restoration plan that includes resiliency and sustainability is extremely important, and this can be achieved through design. Some design considerations that allow for resiliency and sustainability include:
Whale View Point Beach vegetation

Vegetation communities along the coastline may be especially vulnerable due to sea-level rise and storm surges. The Whale View Point Restoration Design project, San Diego, CA.

      • Incorporating variability into grading plans for sites located in close proximity to rivers and oceans. This may include modifying the grade or adding macrotopographic features such as, riprap to counter sea level rise or waddles to address fluctuations in stream flows.
      • Modifying the planting palette to include native plants that were historically abundant as well as some species that may be less abundant but better suited to future conditions such as, drought or salinity-tolerant plants dependent upon the site.
      • Modifying the distribution and placement of plants in response to decreased fresh water flows or increasing salinity intrusion. For example, willows planted too close to the salinity gradient of a brackish water tributary may become displaced within a few seasons by more salt-tolerant shrubs such as coyote-brush and gumplant.
      • Increasing the microtopographic complexity to incorporate various elevations of a site and create multiple small scale habitats. This gives plants the ability to make small scale upslope or downslope shifts if needed over time.
      • Creating north-south corridors during large scale restoration projects to allow plants to shift in latitude dependent upon conditions.

While we may not be able to predict human actions such as how much or how little carbon emissions will change in the forthcoming years, we can assume that climate conditions will change. And as restoration practitioners we can continue to incorporate variability into plans to create more resilient and sustainable habitats.

About the Author

Kate Gazzo Ecologist

Kate Gazzo is an Ecologist for Great Ecology. She specializes in water quality issues and watershed management with experience in invasive species management, wetland delineations, and biological surveys. She recently conducted water quality monitoring associated with agricultural contaminants in California’s central valley.

References

Lenihan, James M., et al. “Response of vegetation distribution, ecosystem productivity, and fire to climate change scenarios for California.” Climatic Change 87.1 (2008): 215-230.

Louis R. Iverson and Anantha M. Prasad 1998. Predicting abundance of 80 tree species following climate change in the eastern United States” Ecological Monographs 68:465–485.

Lavendel, Brian. “Ecological restoration in the face of global climate change: obstacles and initiatives.” Ecological Restoration 21.3 (2003): 199.

Mueller, Rebecca C., et al. “Differential tree mortality in response to severe drought: evidence for long‐term vegetation shifts.” Journal of Ecology 93.6 (2005): 1085-1093.

National Park Service. “Pinyon-Juniper Woodlands-Climate change and Literature Cited”. Accessed March 26, 2015 from http://www.nps.gov/articles/pinyon-juniper-woodlands-climate-change-and-literature-cited.htm

Saxon, E., B. Baker, W. Hargrove, F. Hoffman, and C. Zganjar. 2005. “Mapping environments at risk under different climate change scenarios”. Ecology Letters 8:53–60.

Veloz, S. D., N. Nur, L. Salas, D. Jongsomjit, J. Wood, D. Stralberg, and G. Ballard. 2013. “Modeling climate change impacts on tidal marsh birds: Restoration and conservation planning in the face of uncertainty”. Ecosphere 4(4):49.

Walther, Gian-Reto, et al. “Ecological responses to recent climate change”. Nature 416.6879 (2002): 389-395.

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