by Andrew Walnum
The degradation of ecosystems around the world continues to occur and an increasingly rapid rate. As a relatively new field of ecology, ecological restoration sometimes struggles to find ways to combat the challenges faced by restoring disturbed ecosystems on a local and global scale. At the latest Convention on Biological Diversity (CBD, 2010 in Nagoya, Japan), restoring ecosystems was recognized as one of the most important tools for preventing future loss of bio diversity. Although this field has grown rapidly since the 1980s, many developed countries, especially in Northern Europe, are just starting recognize its importance. Several challenges are needed to be overcome in order to protect biodiversity on a large scale. This study uses northern forests in Europe as an example on what can and needs to be done in order to ensure long-term environmental and biodiversity preservation to reach goals set forth by the CBD.
The basis of this paper comes from discussions held in workshop hosted by PRIFOR; a Nordic work group that focuses on primeval boreal forests. The authors stress that although these discussions concentrated on facing restoration challenges in northern European forests, that the conclusions reached during the workshop can be viewed as a general reference for restoring various forests. They discuss “…the objectives, theory, practice and problems related to ecological restoration of forests.” After summarizing all of these aspects they next identify future challenges that will be faced in forest restoration.
Anthropogenic activities have significantly affected the structure and composition of forests, especially in areas that have been inhabited for long periods of time. Much of this is due to logging or clearing land for agriculture. The overall complexity of forest structure has seen a huge decline resulting in large amounts of habitat loss. For instance, the accumulation of deadwood in old-growth forests led to increased habitat space for fungus and arthropods. These changes have created new species assemblages resulting in more generalist species. It is important to recognize that over that all forests have been shaped by human intervention and are at varying states of “naturalness” and restoration plans must react accordingly.
Currently there are a large number of restoration projects taking place in northern Europe. These projects focus on restoring or improving past ecological function and structure of the forest. Many of these projects focus on restoring the hydrology of an area by blocking off drains using alluvium to raise the water table. Creating open canopies allow for certain trees and plants to reestablish within the forest. Another important implementation is returning regular burning regimes to the ecosystems as was seen in the past. These processes are expensive and represent an extremely small fraction of the total northern forests. However, they help to restore biological diversity to areas and assist in allowing the forest to behave naturally.
An important aspect of restoration ecology is understanding what cannot be restored in a certain ecosystem or location. Climactic, ecological, economical, and sociological challenges may be present that prevent full restoration from taking place. For example, at the forest level, burning may help to reestablish certain plant species but it providing funding for consistent fire regimes is most likely economically out of reach. On the species level, there is a large amount of information that is needed in order to fully maximize the forests ability to maintain a high level of species richness. Practitioners must understand the types of habitats and microclimates needed to restore species richness along with finding corridors that allow species to naturally reestablish a forest ecosystem. In addition, restoration may be entirely feasible in a particular location but is not allowed to occur due to unwanted side-effects such as increased pest numbers and erosion. Currently, it hard to measure the effects of restoration on reaching long-term biodiversity goals. Most studies only show short-term trends in changes in species richness and focus on immediate small scale restoration goals. However, much evidence does support forest restoration as a viable option for increasing biodiversity.
Although still a young field, ecological restoration has learned many lessons as it strives to increase biodiversity and/or restore past ecosystems. For one, ecological knowledge should be focused on the particular target ecosystem that is being restored. Using generalized techniques may not reflect the natural disturbance regimes of the past resulting in little to know changes in biodiversity. Knowledge on each specific ecosystem must be gathered to ensure a complete understanding of restoration goals and practices. Just as important is the issue of defining “naturalness.” Often times species are reintroduced into a target ecosystem based on a historical reference, such as an undisturbed forest. It is important to recognize that all ecosystems have been affected by human contact to various degrees and a “natural” forest may not fully reflect past species trends. Consistently monitoring an ecosystem is also very important for restoration purposes. Monitoring can help a practitioner decided how much effort must be needed to restore and ecosystem. Sometimes, an ecosystem can bounce back from a disturbance naturally and may not need a large amount of funding or resources to restore. Monitoring after restoration is also important for understanding species dynamics and increasing our knowledge of species function within an ecosystem.
There are several challenges relating to forest restoration that must be addressed in the future. The first being unpredictability. Restored ecosystems are often small fragments of a large ecosystem and may be prone to unpredictable stresses that may occur. The role of global climate change may have an unknown effect on a restored ecosystem. Another challenge is the time scale needed for an ecosystem to become self-functioning. These forests may take hundreds of years to reach a point where they no longer need human intervention in order to thrive with high levels of species richness. Despite current restoration efforts, we still do not know if restoration helps lead to a more resilient ecosystem. Social restrictions are also a large challenge that must be faced. It may be difficult to find areas large enough to support a sustainable, self-functioning ecosystem in many areas from fragmentation due to urbanization or landowners refusing to allow restoration on their property.
Despite these challenges, there are global initiatives being implemented to restore large areas of land to increase biodiversity. Restoration ecologists understand what is needed to properly restore ecosystems and there is increasing information about habitats and species assemblage. Planning across administrative levels will help ensure funding and implementation of restoration projects world-wide.
Halme, P., Allen, K.A., Auniņš, A., Bradshaw, R.H., Brūmelis, G., Čada, V., Clear, J.L., Eriksson, A.-M., Hannon, G., Hyvärinen, E., 2013. Challenges of ecological restoration: lessons from forests in northern Europe. Biological Conservation 167, 248-256. http://www.sciencedirect.com/science/article/pii/S0006320713003030