restricted access V.7 Restoration Ecology
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V.7 Restoration Ecology Richard J. Hobbs OUTLINE 1. What is restoration ecology? 2. Concepts in restoration ecology 3. Key steps in ecological restoration 4. Repairing damaged ecosystem processes 5. Directing vegetation change: succession and assembly rules 6. Fauna and restoration 7. Landscape-scale restoration 8. Prevention versus restoration Restoration ecology is the science underpinning the practice of repairing damaged ecosystems. Restoration ecology has developed rapidly over the latter part of the twentieth century, drawing its concepts and approaches from an array of sources, including ecology, conservation biology, and environmental engineering. We are faced with an increasing legacy of ecosystems that have been damaged by past and present activities, and it is increasingly recognized that, in many situations, successful conservation management will need to include some restoration. This may take many different forms, such as the reintroduction of particular species, removal of problem species such as weeds or feral animals, or the reinstatement of particular disturbance regimes (including fire and flood regimes). GLOSSARY alternative stable state. A relatively stable ecosystem structure or composition that is different from what was present before disturbance disturbance. Episodic destruction or removal of ecosystem components resilience. The ability of an ecosystem to recover following disturbance restoration. The process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed succession. The process of vegetation development following disturbance, often characterized by relatively predictable sequences of species replacement over time threshold. A situation where there has been a nonlinear (i.e., sudden or stepped) change in the ecosystem in response to a stress or disturbance, which is often difficult to reverse 1. WHAT IS RESTORATION ECOLOGY? Restoration ecology is the science behind the term ecological restoration, which covers a range of activities involved with the repair of damaged or degraded ecosystems and is usually carried out for one of the following reasons: 1. To restore highly disturbed, but localized sites, such as mine sites. 2. To improve productive capability in degraded production lands. 3. To enhance nature conservation values in protected landscapes. 4. To restore ecological processes over broad landscape-scale or regional areas. Ecological restoration occurs along a continuum, from the rebuilding of totally devastated sites to the limited management of relatively unmodified sites, and hence merges with conservation biology. Restoration aims to return the degraded system to a less degraded state that is valuable for conservation or other use and that is sustainable in the long term. An array of terms has been used to describe these activities, including restoration, rehabilitation, reclamation , reconstruction, and reallocation. Generally, restoration has been used to describe the complete reassembly of a degraded system to its undegraded state complete with all the species previously present, whereas rehabilitation describes efforts to develop some sort of functional or productive system on a degraded site. In addition, some authors use the term reallocation to describe the transfer of a site from one land use to a more productive or otherwise beneficial use. However , the term restoration is often used to refer broadly to activities that aim to repair damaged systems. Ecosystem characteristics to be restored can include the following: 1. Composition: species present and their relative abundances. 2. Structure: vertical arrangement of vegetation and soil components (living and dead). 3. Pattern: horizontal arrangement of system components. 4. Heterogeneity: a complex variable made up of components 1–3. 5. Function: performance of basic ecological processes (i.e., energy, water, nutrient transfers). 6. Species interactions: pollination, seed dispersal, etc. 7. Dynamics and resilience: succession and state-transition processes, recovery from disturbance . Restoration has often been viewed as returning an ecosystem or community back to a previous state, i.e., the ecosystem that existed at the site before human disturbance or alteration. However, ecosystems are naturally dynamic entities, and hence, the setting of restoration goals in terms of static compositional or structural attributes is problematic. Often, past system composition or structure is unknown or partially known, and past data provide only static snapshots of system parameters. Current undegraded reference systems can therefore act as potential reference systems against which the success of restoration efforts in degraded systems can be measured. An alternative approach is to explicitly recognize the dynamic nature of ecosystems and to accept that there is a range of potential short- and long-term outcomes of restoration projects. Increasingly, the focus is on having a transparent and defensible method of setting restoration goals that clarify the desired characteristics for the system in the future rather than in relation...