Degraded or just different? Perceptions and value judgements in restoration decisions

An underlying premise of ecological restoration is that it focuses on the recovery of degraded systems. While this is an apparently straightforward aim, there is in fact considerable variation in how the term “degraded” is defined, used and assessed. In addition, there is a notable subjective component to decisions regarding what is degraded and what isn't, and this often relates to the values and goals being considered. There is likely to be little argument over highly degraded systems where damage and loss of valued characteristics are evident. But where system change is less stark and the changes have mixed benefits and disbenefits, the decision on whether the system is degraded and hence in need of restoration becomes more difficult. As systems continue to change in the face of ongoing climate, land use and other environmental changes, decisions become more difficult regarding which systems are degraded and which are merely different from what was there before. Difference does not necessarily equate to degradation. Effective use of scarce management resources relies on an improved ability to openly debate and resolve such issues.     

What's wrong with novel ecosystems,really?

The novel ecosystems concept has gained much traction in the restoration community. It has also drawn the ire of several prominent ecologists and is the focus of an ongoing debate. We consider three key aspects of this debate: irreversible thresholds, non‐native species, and the hybrid state. Irreversible thresholds have been acknowledged in restoration for years, but predicting when a threshold will be crossed and the degree of reversibility is problematic. Oftentimes reversibility is a function of multiple factors, such as cost and public support. In this sense, a novel ecosystem is not an alternate state but a decision. The need for pragmatism regarding control of non‐natives has also long been recognized in restoration circles. Proponents of the novel ecosystem idea adopt this pragmatism by recommending that management decisions be based on impacts conferred by species in altered ecosystems, regardless of their origin. The concept of a hybrid state has proven difficult to operationalize. We suggest that rather than trying to identify the boundary between hybrid and novel states, ecosystems exist on a gradient of alteration. We offer a decision tree for restoration action that integrates aspects of novel ecosystems with other perspectives in modern restoration ecology. We conclude that the idea of novel ecosystems, though not perfect, deserves a place under the “big tent” of restoration that includes efforts to return fully to a reference state, as well as strategies for reinstating lost ecological processes and enhancing ecosystem services in transformed landscapes where such a return is deemed infeasible.     

Does Acacia dealbata express shade tolerance in Mediterranean forest ecosystems of South America?

The distribution of Acacia dealbata Link (Fabaceae) in its non-native range is associated with disturbed areas. However, the possibility that it can penetrate the native forest during the invasion process cannot be ruled out. This statement is supported by the fact that this species has been experimentally established successfully under the canopy of native forest. Nonetheless, it is unknown whether A. dealbata can express shade tolerance traits to help increase its invasive potential. We investigated the shade tolerance of A. dealbata under the canopy of two native forests and one non-native for three consecutive years, as well as its early growth and photosynthetic performance at low light intensities (9, 30, and 70 μmol m⁻²sec⁻¹) under controlled conditions. We found many A. dealbata plants surviving and growing under the canopy of native and non-native forests. The number of plants of this invasive species remained almost constant under the canopy of native forests during the years of study. However, the largest number of A. dealbata plants was found under the canopy of non-native forest. In every case, the distribution pattern varied with a highest density of plants in forest edges decreasing progressively toward the inside. Germination and early growth of A. dealbata were slow but successful at three low light intensities tested under controlled conditions. For all tested light regimes, we observed that in this species, most of the energy was dissipated by photochemical processes, in accordance with the high photosynthetic rates that this plant showed, despite the really low light intensities under which it was grown. Our study reveals that A. dealbata expressed shade tolerance traits under the canopy of native and non-native forests. This behavior is supported by the efficient photosynthetic performance that A. dealbata showed at low light intensities. Therefore, these results suggest that Mediterranean forest ecosystems of South America can become progressively invaded by A. dealbata and provide a basis for estimating the possible impacts that this invasive species can cause in these ecosystems in a timescale.