James M. Bullock

Enhancement of Biodiversity and Ecosystem Services by Ecological Restoration: A Meta-Analysis

Assessing Ecological Restoration In the wake of the Millennium Ecosystem Assessment, the analysis of ecosystem services, and their relationship to biodiversity, has become one of the most rapidly developing research themes in environmental science. At the same time, ecological restoration is widely being implemented as a response to environmental degradation and biodiversity loss. Rey Benayas et al. (p. 1121, published online 30 July) link these themes in a meta-analysis of the impacts of ecological restoration actions on provision of ecosystem services and biodiversity conservation. The analysis of 89 published restoration projects worldwide establishes that ecological restoration does, in general, have positive impacts on both biodiversity and provision of ecosystem services. These effects are especially marked in the tropics. Thus, ecological restoration actions may indeed deliver benefits, both in terms of biodiversity conservation and supporting human livelihoods. Restoration, biodiversity, and ecosystem services are positively linked in a wide range of ecosystem types across the globe. Ecological restoration is widely used to reverse the environmental degradation caused by human activities. However, the effectiveness of restoration actions in increasing provision of both biodiversity and ecosystem services has not been evaluated systematically. A meta-analysis of 89 restoration assessments in a wide range of ecosystem types across the globe indicates that ecological restoration increased provision of biodiversity and ecosystem services by 44 and 25%, respectively. However, values of both remained lower in restored versus intact reference ecosystems. Increases in biodiversity and ecosystem service measures after restoration were positively correlated. Results indicate that restoration actions focused on enhancing biodiversity should support increased provision of ecosystem services, particularly in tropical terrestrial biomes.

Costs of dispersal

Dispersal costs can be classified into energetic, time, risk and opportunity costs and may be levied directly or deferred during departure, transfer and settlement. They may equally be incurred during life stages before the actual dispersal event through investments in special morphologies. Because costs will eventually determine the performance of dispersing individuals and the evolution of dispersal, we here provide an extensive review on the different cost types that occur during dispersal in a wide array of organisms, ranging from micro‐organisms to plants, invertebrates and vertebrates. In general, costs of transfer have been more widely documented in actively dispersing organisms, in contrast to a greater focus on costs during departure and settlement in plants and animals with a passive transfer phase. Costs related to the development of specific dispersal attributes appear to be much more prominent than previously accepted. Because costs induce trade‐offs, they give rise to covariation between dispersal and other life‐history traits at different scales of organismal organisation. The consequences of (i) the presence and magnitude of different costs during different phases of the dispersal process, and (ii) their internal organisation through covariation with other life‐history traits, are synthesised with respect to potential consequences for species conservation and the need for development of a new generation of spatial simulation models.

Restoration of ecosystem services and biodiversity: conflicts and opportunities

Ecological restoration is becoming regarded as a major strategy for increasing the provision of ecosystem services as well as reversing biodiversity losses. Here, we show that restoration projects can be effective in enhancing both, but that conflicts can arise, especially if single services are targeted in isolation. Furthermore, recovery of biodiversity and services can be slow and incomplete. Despite this uncertainty, new methods of ecosystem service valuation are suggesting that the economic benefits of restoration can outweigh costs. Payment for Ecosystem Service schemes could therefore provide incentives for restoration, but require development to ensure biodiversity and multiple services are enhanced and the needs of different stakeholders are met. Such approaches must be implemented widely if new global restoration targets are to be achieved.

Long distance seed dispersal by wind : measuring and modelling the tail of the curve

Abstract The size and shape of the tail of the seed dispersal curve is important in determining the spatial dynamics of plants, but is difficult to quantify. We devised an experimental protocol to measure long-distance dispersal which involved measuring dispersal by wind from isolated individuals at a range of distances from the source, but maintaining a large and constant sampling intensity at each distance. Seeds were trapped up to 80 m from the plants, the furthest a dispersal curve for an individual plant has been measured for a non-tree species. Standard empirical negative exponential and inverse power models were fitted using likelihood methods. The latter always had a better fit than the former, but in most cases neither described the data well, and strongly under-estimated the tail of the dispersal curve. An alternative model formulation with two kernel components had a much better fit in most cases and described the tail data more accurately. Mechanistic models provide an alternative to direct measurement of dispersal. However, while a previous mechanistic model accurately predicted the modal dispersal distance, it always under-predicted the measured tail. Long-distance dispersal may be caused by rare extremes in horizontal wind speed or turbulence. Therefore, under-estimation of the tail by standard empirical models and mechanistic models may indicate a lack of flexibility to take account of such extremes. Future studies should examine carefully whether the widely used exponential and power models are, in fact, valid, and investigate alternative models.

Creating woodland islets to reconcile ecological restoration, conservation, and agricultural land use

Restoration initiatives seek to address widespread deforestation and forest degradation, but face substantial problems. “Passive restoration”, whereby abandoned agricultural land undergoes secondary succession, is often slow, owing to biotic and abiotic limitations. “Active restoration”, chiefly accomplished by planting trees, can be very expensive if large areas are to be restored. We suggest “woodland islets” as an alternative way to achieve ecological restoration in extensive agricultural landscapes, particularly in low-productivity environments. This approach involves the planting of many small, dense blocks of native trees to enhance biodiversity and provide a range of ecosystem services. If the surrounding land is abandoned, the islets act as sources of woodland species and seed, which can accelerate woodland development. Alternatively, if the surrounding area is used for cultivation or pasture, the islets will increase the conservation value of the land and offer the potential for income generation. Here, we review existing approaches to woodland restoration and evaluate the relative strengths and weaknesses of the woodland islets approach.

GENETIC VARIATION IN DEFENSE CHEMISTRY IN WILD CABBAGES AFFECTS HERBIVORES AND THEIR ENDOPARASITOIDS

Populations of wild Brassica oleracea L. grow naturally along the Atlantic coastlines of the United Kingdom and France. Over a very small spatial scale (i.e., <15 km) these populations differ in the expression of the defensive compounds, glucosinolates (GS). Thus far, very few studies have examined interactions between genetically distinct populations of a wild plant species and associated consumers in a multitrophic framework. Here, we compared the development of a specialist (Pieris rapae) and a generalist (Mamestra brassicae) insect herbivore and their endoparasitoids (Cotesia rubecula and Microplitis mediator, respectively) on three wild populations and one cultivar of B. oleracea under controlled greenhouse conditions. Herbivore performance was differentially affected by the plant population on which they were reared. Plant population influenced only development time and pupal mass in P. rapae, whereas plant population also had a dramatic effect on survival of M. brassicae. Prolonged development time in P. rapae corresponded with high levels of the indole GS, neoglucobrassicin, whereas reduced survival in M. brassicae coincided with high levels of the aliphatic GS, gluconapin and sinigrin. The difference between the two species can be explained by the fact that the specialist P. rapae is adapted to feed on plants containing GS and has evolved an effective detoxification system against aliphatic GS. The different B. oleracea populations also affected development of the endoparasitoids. Differences in food-plant quality for the hosts were reflected in adult size in C. rubecula and survival in M. mediator, and further showed that parasitoid performance is also affected by herbivore diet.

An experimental study of the effects of sheep grazing on vegetation changes in a species-poor grassland and the role of seedling recruitment into gaps

An experiment was set up in 1986 on a species-poor grassland in Oxfordshire to determine the effect of sheep grazing management on vegetation change after cessation of fertilizer applications. Three seasons of grazing (winter, spring and summer) were applied, each with two grazing intensities, in a 2 × 2 × 2 factorial design with two blocks in 16 paddocks. Point quadrat surveys in 1990 showed that the grassland vegetation was dominated by perennial grasses and that the frequency distribution of species was highly skewed. Dicotyledonous species («dicots») were extremely rare, having an overall frequency of only 0.43%

Measuring plant dispersal: an introduction to field methods and experimental design

The measurement of plant dispersal is vital for understanding plant distribution and abundance at different scales. However, dispersal is difficult to measure and there is a lack of guidance for researchers new to the subject. In this paper we provide advice on methods for measuring dispersal in the field and approaches to experimental design. First, we encourage clear exposition of the aims of the dispersal study and the ultimate use to which the data will be put (e.g. local dynamics, invasion processes, etc). We outline the types of dispersal exhibited by plants and emphasise that many species are dispersed by multiple processes, which are not necessarily related to putative adaptations. Few studies properly address the full range of processes by which a species is dispersed. We review methods for measuring plant dispersal, summarising the type of dispersal measured and problems with each method. We then outline the major questions about effort to be considered in sampling protocols and present an optimisation algorithm for designing dispersal studies given a suite of options, and biological and resource constraints. We propose and demonstrate a simulation modelling approach to comparing the data quality obtained by alternative experimental designs. Integrating simulation models with pilot studies offers a rapid route to improved estimation methods. We then discuss functions commonly fit to dispersal data and recommend caution as none is a priori the best description of the dispersal process. Finally, we call for a better description and understanding of dispersal kernels by: a more rigorous approach to designing dispersal measurement; better targeting of dispersal studies to particular questions; and achieving a deeper understanding of the mechanisms underlying dispersal, so that we can move from descriptions of pattern to a grasp of process.

Performance of generalist and specialist herbivores and their endoparasitoids differs on cultivated and wild Brassica populations.

Through artificial selection, domesticated plants often contain modified levels of primary and secondary metabolites compared to their wild progenitors. It is hypothesized that the changed chemistry of cultivated plants will affect the performance of insects associated with these plants. In this paper, the development of several specialist and generalist herbivores and their endoparasitoids were compared when reared on a wild and cultivated population of cabbage, Brassica oleracea, and a recently established feral Brassica species. Irrespective of insect species or the degree of dietary specialization, herbivores and parasitoids developed most poorly on the wild population. For the specialists, plant population influenced only development time and adult body mass, whereas for the generalists, plant populations also affected egg-to-adult survival. Two parasitoid species, a generalist (Diadegma fenestrale) and a specialist (D. semiclausum), were reared from the same host (Plutella xylostella). Performance of D. semiclausum was closely linked to that of its host, whereas the correlation between survival of D. fenestrale and host performance was less clear. Plants in the Brassicaceae characteristically produce defense-related glucosinolates (GS). Levels of GS in leaves of undamaged plants were significantly higher in plants from the wild population than from the domesticated populations. Moreover, total GS concentrations increased significantly in wild plants after herbivory, but not in domesticated or feral plants. The results of this study reveal that a cabbage cultivar and plants from a wild cabbage population exhibit significant differences in quality in terms of their effects on the growth and development of insect herbivores and their natural enemies. Although cultivated plants have proved to be model systems in agroecology, we argue that some caution should be applied to evolutionary explanations derived from studies on domesticated plants, unless some knowledge exists on the history of the system under investigation.

Translocations of native species in the UK : implications for biodiversity

Native species are translocated for conservation, commercial, amenity and research purposes. These activities are related, and need to be considered and planned in terms of their effects on biodiversity. Procedures for assessing, implementing and regulating translocations have, however, been subject to largely uncoordinated development; recommendations or guidelines being produced separately for each area of expertise. There is a need to pull together the profuse information concerning specific translocations in order to present a broad approach to the general problems and concerns. Here, the extent and nature of translocations of native species within the UK are reviewed, and recommendations for policy and legislation are made in the context of those currently in use in the UK. The recommendations include the following: (i) improvement of the ways in which relevant information is disseminated; (ii) ease of implementation should be a prime consideration; and (iii) formation of new policy and guidelines should include all UK and international organizations involved in carrying out, advising on, or licensing translocations.