Meeting Nature Halfway: Adapting to Climate Species Migration in Restoration

Ecological restoration as a study, act, and framework exists on a dynamic platform. The considerations required for the creation of a successful, thriving ecosystem from a depleted area are endless, and thus perfection can never be achieved – only strived for. Among the countless other factors, one must account for the idiosyncrasies of species planted on the site– their successional preferences, their growth patterns, their interactions with other flora and fauna, their habitat preferences. Generally speaking, trees operate on a slower scale than animals and other annual plants. While wild red raspberry and other herbaceous vegetation proliferate by producing seed and growing and re-growing every year, adapting quickly to changing conditions, trees can live on scales of hundreds of years. As best understood by professional tree climber and filmographer James Aldred, “[Trees] inhabit a different timescale than we do and … the life of one tree can easily span dozens of human generations.” While life and death and responding to stresses are just part of the long, slow, and turbulent activities of forest systems, ecological restoration and management strives to optimize these processes and ensure the best survival for as many trees as possible, giving the system a head start towards achieving its own unique equilibrium. Aldred also said, “All nature needs is to be met halfway; it’ll manage the rest.” The act of restoration requires a long-term perspective.

What happens, then, when these carefully studied understandings about the ideal conditions for plant growth are faced with a new, large, and rapidly encroaching threat? Climate change is being felt in various scales across ecosystems globally, creating resounding implications for known ecological restoration methods.

While these implications branch into dozens of impacts, far too extensive to be elaborated here, the stresses of rapid local climate change on species is already being felt in catastrophic proportions. For example, in Southern Ontario, ticks are on the move. Field technicians that only witnessed small populations in the past are now tweezing the Lyme-disease-carriers off of their skin daily. These ticks, which thrive in warm weather, are thriving from the increased non-dormant seasons of their hosts. Ticks are an embodiment of a global phenomenon of re-emerging diseases that were previously kept under control, but are now proliferating under warmer conditions. Tropical diseases are transmitted with the expanding ranges of these ticks. These range changes mobile species, especially migrating birds, are relatively easy depict with tracking technologies and citizen science projects like eBird, where birders can record their sightings.

However, trackers cannot be placed on the millions of seedlings that are released from trees, each aspiring to find the ideal location of growth to achieve the same, or greater, reproductive health of their mother tree. With the limited mobility of plants, and the inability to easily track their movements, the species migration of flora continue to be an enigma. The USDA Forest Service reports that tree species migration rates have increased from 1km/decade since the last post-glacial period to up to 4.3km/decade. Plants are limited in their ability to migrate to new optimal habitats for growth by several factors, including their seed dispersal ability, the preferred conditions for growth (for example, level of shade tolerance, soil acidity, moisture, to name but a few), as well as available pathways for migrating. Habitat fragmentation and the loss of ecological corridors from urban development can trap species within their rapidly-changing environments. This poses the threat of local extirpation, the loss of species that have dwelled in the region for centuries. While animals that face adverse conditions have the option to attempt to flee, plants must remain stationary and undergo energy-intensive measures of bracing themselves and ensuring the survival of their offspring in more preferable habitats. Prevention of these extirpations demands assisted dispersal, effectively accomplished with ecological restoration with a focus on the adaptability of the planted species.

South-Eastern Ontario, Canada and its surrounding regions have been home to prosperous sugar maple (Acer saccharum) stands throughout its history, playing a vital part in establishing its reputation as an iconic maple syrup producer. The prominence of these stands in the area makes sugar maple one of the most heavily researched hardwood trees in the region. Sugar maple and other hardwoods like trembling aspen and paper birch are more responsive to the predicted water stresses due to the region from climate change, and are thereby likely to migrate poleward. Multiple studies predict that sugar maple stands in Southern Ontario will be extirpated as soon as the year 2100, with resounding implications on maple syrup industries that have been established there for years. With climate modelling approaches, it is predicted that nearly half of the species found in the area are at risk for extirpation without migration. Instances of changing climates that make unsuitable conditions for agricultural crops that have been historically planted in areas for generations are not uncommon around the globe, and some farmers are opting for more adaptive and stress-tolerant crops. A similar approach is needed for ecological restoration.

The choice of species to plant in restoration sites is now crucial under these climate stresses. These choices no longer only require consideration of habitat preferences, but also: plasticity, long-range dispersal ability, ability to respond to water stresses, extent of surrounding habitat fragmentation, responses to irregular seasonal changes like increased free-thaw cycles and longer warm or cold periods, known or predicted invasion of pests. All these factors and more are being used by researchers to create climate models that predict the movement of these species over time. These models are imperfect and largely contested – nearly all studies cite uncertainty of the effects of climate change as the largest limiting factor of the predictions. Nonetheless, these models are continuously hybridizing and improving, all pointing us to the necessity of creating pathways for at-risk, enclosed species to migrate through in order to preserve biodiversity.

Restoration ecologists need to find a balance between the planting of both hardy and sensitive species, of preserving known ecosystems and allowing novel ones to emerge, of using known restoration methods and understanding that new non-intuitive ones need to be developed in these changing conditions. Climate change adaptation is becoming a non-negotiable aspect of successful restoration.

By Earth Restoration Service Blog Writer Hashveenah Manoharan

Images taken from Wikimedia Commons