Forward–Looking Forest Restoration Under Climate—Are U.S. Nurseries Ready?

Scientists have predicted that climate change-induced variations in precipitation levels and temperature will result in range shifts for tree species across the United States. Therefore, many land managers are beginning to assess climate change predications when planning restoration plantings by increasing the proportion of plant species that will be favored under climate change. As such, forward-looking restoration will involve selecting varieties of species adapted to warmer conditions and variable rainfall levels. State nurseries often supply the species for restoration activities undertaken by state natural resources agencies and land trusts that require hundreds or thousands of saplings of one or more species. Tepe and Meretsky (2011) investigated whether state and large-scale commercial nurseries currently offer species that would support forward-looking restoration. The authors collected information about state and commercial nurseries in the 48 contiguous and subdivided the nurseries into region units. The results indicate that of 30 state nurseries, only 20% claimed they considered climate change when planning for which tree species to carry. However, 26 nurseries (87%) stated that they carried species with ranges that extended south of their state. At least 21% of nurseries that did not plan for climate change mentioned that they would like to, while approximately 13% stated that they introduced or researched new species tolerant to new climate conditions. Barriers to forward-planning restoration included customer demand, policies and laws regarding seed zones, and the uncertainty regarding the future climate. Ultimately, researchers, policy makers, nursery managers, land managers, and nursery clients must discuss how predicated future climate change will affect forests, how nurseries can work within the legal framework to plan for future conditions, and how clients can be encouraged to plant tree species that are tolerant to future predicated climatic conditions.—Megan Smith.
Tepe, T.L, and Vicky J. Meretsky, 2011. Forward–Looking Forest Restoration Under Climate Change—Are U.S. Nurseries Ready? Restoration Ecology: 19(3), 295–298. DOI: 10.1111/j.1526-100X.2010.00748.x

Forest restoration involving tree planting takes place after the conservation purchase of farm and pastureland. Additionally, it follows forest harvest or disturbances such as forest fire or damage from ice storms or tornadoes. Reforestation during early successional stages allows land managers to shift species composition of the resulting forest in a way that could accommodate climate change. However, the process of forward-looking restoration requires a source of trees that may not be native to the restoration site or to the state.
To assess if state nurseries offer species that would support forward-looking restoration, the authors obtained information concerning state and commercial nurseries in the 48 contiguous states from November 2008 to May 2009. Tepe and Meretsky determined which states had state nurseries using Internet searches. They then contacted each nursery or state forestry agency and spoke to at least one state nursery in every state with state nurseries (n = 31). Nurseries were asked whether they currently sold species whose ranges extended south of the state boundaries (species able to tolerate warmer conditions than those found in the state), and whether climate change was considered when stocking the nursery. The nurseries were then subdivided into region units. A map displaying the division of states used in regional analysis was constructed.
Additionally, the authors contacted commercial nurseries within each region based on recommendations from the state nursery staff and forestry practitioners. These commercial nurseries (n = 8) are of adequate size to provide stock for large-scale plantings. The authors also asked about the availability of species with ranges south of the nursery location, and about climate change considerations regarding the choice of nursery stock.
            Tepe and Meretsky found that of the 48 original states, 30 states had one or more state nurseries. Southeastern states were more likely than southwestern states to have them. Of these 30 state nurseries, 6 (20%) stated that they considered climate change when planning for which tree species to carry. However, climate change considerations were rarely in use in all the regions. Only one in eight commercial nurseries suggested that they considered climate change in planning. In contrast, approximately 87% of nurseries claimed they carried species with ranges that extended south of their state.
            Five nurseries out of the 24 nurseries that did not plan for climate change mentioned that they were thinking about doing so or would like to do so. Eight nurseries not planning for climate change were aware of academic discussions regarding climate change affecting forests. Two nurseries said climate change was not among the issues they would consider in the near future. Interestingly, four state nurseries (13%) stated they considered disease-tolerant species and another four stated they introduced or researched introducing new species and individuals tolerant to new climate conditions. Eight nurseries mentioned climate regions, seed zones, and accompanying regulations as barriers to planning for climate change. Other nurseries claimed that planning for customer demand was a priority over other planning considerations. Finally, two nurseries mentioned the possibility of a carbon market increasing demand for trees and changing the species that would be in demand. A histogram displaying the ratios of states in region, states with nurseries, and nurseries incorporating climate change was constructed.
 These results demonstrate that most state nurseries are not actively planning for climate change. Most have not addressed the implications climate change may have for their industry or for their ability to provide trees to restore forests under climate change scenarios. Western states have the largest proportion of state nurseries planning for climate change, which may reflect the climate change impacts already affecting forest health in this region. Yet, not all nurseries in the west are planning for climate change.
Although many nurseries lack active planning in regards to climate change, many nurseries carry more than 10 tree species in their stock that have ranges south of state boundaries. This reflects the practice among nurseries of obtaining tree stock from 240 kilometers south of their planting areas.
Overall, nurseries mentioned three major obstacles to adapting to climate change. The first involved uncertainty regarding what the state’s future climate would be. The second took into account the existence of current laws or policies constraining planting decisions, which in part influenced the third obstacle: client demand for traditional seed stock.
Policies related to seed zones were identified as a constraint to using or supplying seed stock other than local genetic and climatic variants. Seed zones are regions that are uniform in climate and soils. They were first established by western states to maximize the success in planting and to minimize the dilution of adapted genotypes. If enforced, only seeds originating in a particular zone can be used for plantings in that zone. Yet, climate change is predicted to establish new conditions and ecosystems, and seed zones are not currently responsive to climate change. Forward-looking restoration that uses a mix of genetic material to produce resilient flora may have better success than restoration limited by present seed zones. Ultimately, changing existing laws and policies will require efforts involving researchers, policy makers, nursery managers, land managers, and other nursery clients. These groups should assess how predicted climate conditions will affect forests, how nurseries can work within the current or revised legal frameworks and plant for future climatic conditions, and how clients can be encouraged to plant climate-change tolerant tree species.
The most promising forward-looking restoration strategy involves planting with a diverse species mix so that each species is favored by some, but not all, likely future climatic conditions. Despite the obstacles described above, some nurseries have been coordinating with geneticists and other researchers to experiment with genotypes that may be more resilient to temperature and moisture extremes. 

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