Designing nature reserves in the face of uncertainty

Conservation reserves are a fundamental tool for managing biodiversity. The so-called SLOSS debate--should we have a Single Large Or Several Small reserves - is central to conservation theory. Population dynamic models suggest that the design that minimizes the risk of extinction of a species is case-specific, with the optimal number of reserves ranging between one and very many. Uncertainty is pervasive in ecology, but, the previous analyses of the SLOSS debate have not considered how uncertainty in the model of extinction risk might influence the optimal design. Herein, we show that when uncertainty is considered, the SLOSS problem is simplified and driven more by the aspirations of the manager than the population dynamics of the species. In this case, the optimal solution is to have in the order of twenty or fewer reserves for any species. This result shows counter-intuitively that considering uncertainty actually simplifies rather than complicates decisions about designing nature reserves.     

The measure of order and disorder in the distribution of species in fragmented habitat

Species distribution patterns within naturally fragmented habitat have been found to often exhibit patterns of pronounced nestedness. Highly predictable extinction sequences are implied by these nested species distribution patterns, thus the patterns are important to both the philosophy and practice of conservation biology. A simple thermodynamic measure of the order and disorder apparent in the nested patterns is described. The metric offers (i) a measure of the uncertainty in species extinction order, (ii) a measure of relative populational stabilities, (iii) a means of identifying minimally sustainable population sizes, and (iv) an estimate of the historical coherence of the species assemblage. Four presumptions govern the development of the metric and its theory: (i) the fragmented habitat was once whole and originally populated by a single common source biota, (ii) the islands were initially uniform in their habitat heterogeneity and type mix, and have remained so throughout their post-fragmentation history, (iii) no significant clinal (latitudinal) gradation exists across the archipelago so as to promote species turnover across the archipelago, and (iv) all species of interest are equally isolated on all islands. The violation of these conditions promotes species distributions which are idiosyncratic to the general extinction order expected in fragmentation archipelagos. While some random variation in extinction order is to be expected, idiosyncratic distributional patterns differ from randomness and are readily segregatable from such noise. A method of identifying idiosyncratic species and sites is described.     

The effect of insularity on the diversity of land birds in the Fiji islands: implications for refuge design

Ecologists have argued over rules of thumb that could be used to set priorities in configuring systems of reserves for preserving biological diversity. To evaluate these simple strategies, I assembled a particularly large and comprehensive data set on the land birds of the Fiji archipelago. I analyzed the species distribution on 220 islands to compare the running total of species preserved by differènt sequences of adding nature reserves to a hypothetical reserve system, treating each island as if it were a potential reserve. A strategy of maximizing the number of islands contributing to any given reserve area (maximum fragmentation) is much more effective at including species than a strategy of maximizing the size of the island components of a reserve (minimum fragmentation). Nevertheless the maximum fragmentation strategy is not a very good one. It is less effective than many random strategies, especially when about 2–10% of total area is to be set aside as reserve, and when only rare species are considered. A computer program was used to determine an optimal strategy by maximizing the number of additional species added for each unit of area added. This strategy is always substantially more effective at encompassing species diversity than either the maximum or minimum fragmentation strategies. It is suggested that the poor performance of the minimum fragmentation strategy is due principally to the presence of many smaller-island endemics within the Fiji archipelago. More generally, it is argued that the effect of fragmentation on species diversity depends on the geographic scale and isolation of the region under consideration. In these respects the Fiji Archipelago may be a particularly good model for continental reserve systems.     

Species diversity preserved in different numbers of nature reserves of the same total area

The expected number of species occurring in different numbers of reserves of the same total area is examined on different assumptions of the spatial distribution and the probability of extinction. The advantage of one large reserve or several smaller ones of equal total area depends on the spatial distributions of species and the stage after the establishement of reserves. In general, several smaller reserves maintain more species immediately after the establishments unless the spatial distribution are uniform or random, whereas one large reserve excels several smaller ones after some rare species have gone extinct unless the spatial distributions are strongly contagious. Since the extinction of rare species must be facilitated as the size of each reserve reduces, the area of a reserve should be larger than the critical area that ensures the persistence of the species. Hence it is concluded that one or a few large reserves are a better strategy in order to maintain the species diversity.     

Landscape patterns and plant species diversity of forest reserves in the Kanto region, Japan

Plant species richness of twenty old-growth forest reserves in the cool-temperate zone in the Kanto region, Japan were investigated to detect the effect of forest fragmentation. The species richness of trees and forest floor plants were analyzed by multiple regression models relating to nine variables on the characteristics of landscape, local habitat and forest stand. The total species diversity did not have a significant correlation with any variables of landscape patterns. In this study, single large reserve in the SLOSS discussion did not seem very effective to preserve more species. However, forest reserves in large patches tend to have relatively infrequent species. Large patches of natural forests were regarded as one of the important factors to preserve infrequent species.     

Evidence for rapid faunal changes on islands in a man-made lake

Summary Few studies of island biogeography have been made on islands in which the time of insularization is precisely known. We tested the effects of island formation on ant species diversity in a man-made lake in South Africa, to determine whether island effects are detectable after only 16 years of insularization. The number of ant species observed at trap-line censuses on islands was significantly correlated with island size (r=0.608; P<0.05) and ant species diversity was generally low compared with similar mainland habitats. Mean species number for all islands, including landbridge islands, was 5.5±3.3 species, and on mainland sites was 7.9±2.85 species. Island effects were more marked on islands <20 ha, which had a mean of 3.3±2.5 species per island. Species number on islands was inversely related to densities of the aggressive Anoplolepis custodiens and A. steingroeveri. These two species were only patchily distributed on mainlands, but these ants were nearly ubiquitous on small islands. Several lines of evidence suggest that this single species domination may be responsible for island effects. Island sites also differed in the number of ant species in different trophic groupings, tending to have fewer granivorous species than the mainland sites, but species in other diet groups were similar in both island and mainland habitats. We conclude that there have been marked changes in the ant faunas on islands smaller than 20 ha apparently due to changes in abundance of the dominant ant species. However, the causes of these changes are unknown.     

A probabilistic model of reserve design

We develop a probabilistic approach to optimum reserve design based on the species-area relationship. Specifically, we focus on the distribution of areas among a set of reserves maximizing biodiversity. We begin by presenting analytic solutions for the neutral case in which all species have the same colonization probability. The optimum size distribution is determined by the local-to-regional species richness ratio k. There is a critical k(t) ratio defined by the number of reserves raised to the scaling exponent of the species-area relationship. Below k(t), a uniform area distribution across reserves maximizes biodiversity. Beyond k(t), biodiversity is maximized by allocating a certain area to one reserve and uniformly allocating the remaining area to the other reserves. We proceed by numerically exploring the robustness of our analytic results when departing from the neutral assumption of identical colonization probabilities across species.     

BIODIVERSITY RESEARCH: Nestedness for different reasons: the distributions of birds,lizards and small mammals on islands of an inundated lake

Aim We examined whether the community compositions of birds, lizards and small mammals were nested in a fragmented landscape in the Thousand Island Lake, China. We also assessed whether the mechanisms influencing nestedness differed among these taxonomic groups. Location Thousand Island Lake, China. Methods Presence/absence matrices were compiled for birds (42 islands) and lizards (42 islands) using line‐transect methods, and for small mammals (14 islands) using live‐trapping methods from 2006 to 2009. Nestedness was analysed using BINMATNEST, and statistical significance was assessed using the conservative null model 3. We used Spearman rank correlations and partial Spearman rank correlations to examine associations of nestedness and habitat variables (area, isolation, habitat diversity and plant richness) as well as life‐history traits (body size, habitat specificity, geographical range size and area requirement) related to species extinction and immigration tendencies. Results The community compositions of birds, lizards and small mammals were all significantly nested, but the causal factors underlying nestedness differed among taxonomic groups. For birds, island area, habitat specificity and area requirement were significantly correlated with nestedness after controlling for other independent variables. For lizards, habitat heterogeneity was the single best correlate of nestedness. For small mammals, island area, habitat heterogeneity and habitat specificity were significantly correlated with nestedness. The nested patterns of birds, lizards and small mammals were not attributable to passive sampling or selective colonization. Main conclusions The processes influencing nested patterns differed among taxonomic groups. Nestedness of bird assemblages was driven by selective extinction, and lizard assemblage was caused by habitat nestedness, while nestedness of small mammals resulted from both selective extinction and habitat nestedness. Therefore, we should take taxonomic differences into account when analysing nestedness to develop conservation guidelines and refrain from using single taxa as surrogates for others.     

Effects of habitat fragmentation and isolation on species richness: evidence from biogeographic patterns

Summary Habitat subdivision by geography or human activity may be an important determinant of regional species richness. Cumulative species-area relationships for vertebrates, land plants, and insects on island archipelagoes show that collections of small islands generally harbor more species than comparable areas composed of one or a few large islands. The effect of the degree of habitat subdivision in increasing species richness appears to increase with the distance from potential sources of colonists. Mountaintop biotas show no clear differences between species richness on large alpine areas and collections of smaller peaks. National park faunas generally have more species in collections of small parks than in the larger parks. In all cases where a consistent effect of subdivision is observed, the more subdivided collection of islands or isolates contains more species. To the degree that these data provide guidance for establishing nature reserves, they suggest that increasing the numbers of reserves may be an important component of conservation strategies.     

Size of nature reserves: densities of large trees and dead wood indicate high value of small conservation forests in southern Sweden

The optimal size of nature reserves has been debated for some time. Although edge and core habitats are often recognized, it is commonly assumed in theory and in studies of a particular habitat type that reserves or patches of different sizes have similar habitat structure. However, for older, highly fragmented landscapes it has been suggested that small areas are of conservation interest as high-quality remnants, whereas large areas are more degraded. We studied 49 randomly selected forest reserves in the size range 5–230 ha (typical for many highly fragmented landscapes) and 3653 sites of key habitat (unprotected deciduous broadleaf forest). Structures in forest that are generally correlated with value for biodiversity were measured, and reserve objectives were examined from declaration texts. Both the density of large trees and the density of dead wood (snags, logs) decreased with increasing reserve size. The mean size of identified key habitats was very small (1.6 ha). A botanical objective for establishment of reserves was more frequently used for smaller reserves. In contrast, cultural and especially recreational objectives were more commonly used when larger reserves were established, suggesting higher values for recreation in these reserves. For vascular plants, birds and beetles, a literature review indicated that small forest patches do not contain impoverished communities, but are often rich (per unit of area). Small reserves and key habitats have several disadvantages, but they are probably important components of reserve networks for biodiversity in highly fragmented landscapes.     

Biodiversity and biogeographic affiliation of Bryozoa from King George Island (Antarctica)

King George Island (KGI), which is located between the Antarctic and South American continents, may play a crucial role in the exchange of Bryozoa amongst the various Antarctic sectors and across the Polar Front. Knowledge regarding the biological diversity of this area could help us understand the evolution of the Antarctic ecosystem and its connectivity to the South American continent as well as the colonization ability of particular species. Here, we investigate the patterns of diversity and biogeographic affiliation of the cheilostome Bryozoa from KGI and the surrounding areas. Of 114 identified taxa from a depth range of 6–492 m, 26 species were reported for the first time in KGI. The most speciose genera were Camptoplites, Osthimosia, Smittina, and Cellarinella. Species richness at KGI consisted of 70% of the total bryozoans at the South Shetland Islands (SSI). Fifty-nine per cent of the bryozoans from KGI are endemic to Antarctica, which closely reflects the previously estimated endemism rate for bryozoans and other Antarctic taxa. Cluster analysis indicated that the strongest faunal links of SSI bryozoans were with Antarctic Peninsula assemblages, corresponding to the physical distance between both locations. The biogeographic similarities between SSI and South America confirm the broad trend of existing Antarctic–South American faunal links previously observed in bryozoans and many other taxa and indicate that SSI might be an important transitional zone between Antarctica and South America.     

云南哀牢山、无量山国家级自然保护区蝴蝶种群动态及多样性

蝴蝶是无脊椎动物中最受关注的类群和环境指示生物之一, 其种群动态及群落结构能快速地反映环境的状况。哀牢山和无量山国家级自然保护区具有复杂多样的生境, 含有丰富的动植物资源。为了有效地保护环境和资源, 2016‒2018年在这两个自然保护区开展了蝴蝶资源及其种群动态的研究。结果表明: 两地蝴蝶均具有较高的多样性水平, 且哀牢山蝴蝶多样性较无量山丰富。哀牢山共观测记录5科83属149种, 该地蝴蝶Shannon-Wiener指数(H_s′)为3.92, 物种丰富度为16.36, Simpson指数为0.97; 景东县无量山样区共记录蝴蝶5科88属143种, Shannon-Wiener指数(H_s′)为3.64, 物种丰富度为15.04, Simpson指数为0.96。哀牢山、无量山两个样区共有5科99属178种蝴蝶。生境分析表明两地蝴蝶均具有明显的垂直分布特征, 哀牢山蝴蝶主要分布在海拔1,100 m以下, 而无量山蝴蝶主要分布在1,100-1,400 m之间。调查时段分析表明, 两地蝴蝶主要分布在5-9月, 哀牢山8月蝴蝶种类较丰富, 而无量山9月蝴蝶种类较丰富。年份分析表明, 哀牢山、无量山两地均以2016年蝴蝶多样性最丰富, 这与适宜的气候及较弱的人为干扰有密切的关系。两地蝴蝶群落为中等相似, Jaccard相似性系数为0.64, 共有种有114种(64.05%)。鉴于无量山、哀牢山蝴蝶多样性较丰富, 且有13种近危物种、3种易危物种和56种个体数极低(≤ 10头)的未列入红色名录的物种, 因此蝴蝶保护工作刻不容缓。     

But is it progress? On the alleged advances of conservation biology over ecology

As conservation biology has developed as a distinct discipline from ecology, conservation guidelines based on ecological theory have been largely cast aside in favor of theory-independent decision procedures for designing conservation reserves. I argue that this transition has failed to advance the field toward its aim of preserving biodiversity. The abandonment of island biogeography theory in favor of complementarity-based algorithms is a case in point. In what follows, I consider the four central objections raised against island biogeographic conservation guidelines, arguing that they fail to undermine the credibility of this framework as a conservation tool. At best, these objections call for a more careful application of this framework to conservation problems, not its wholesale abandonment. At the same time, complementarily-based algorithms are biased in favor of networks of small reserves containing non-overlapping species. These conditions threaten to promote inbreeding depression, genetic drift and other factors that increase a population’s risk of extinction. Therefore, recent developments in the field of conservation biology have arguably not contributed to its ultimate aim of preserving the maximum amount of biodiversity in the long run.

Designing nature reserves: traditional criteria may act as misleading indicators of quality

Traditionally, numerous criteria have been used for selecting valuable areas for the establishment of nature reserves. In most cases these criteria are applied indiscriminately with the assumption that their generalized use gives them universal validity. In this study we test the value of different variables (area and shape of patches of natural vegetation, degree of internal fragmentation, and diversity of habitats at the periphery of patches) at the landscape level as indicators of plant richness and diversity, and relative abundance of native plants, in a group of natural vegetation relicts ranging from 0.004 km² to 1.027 km² and surrounded by sub-urban and industrial settings. Species richness, diversity, and number of native and exotic species increased with the area of the patches. The shape of the patch was the second most important variable to influence species richness and diversity. The number of exotic species increased with increasing numbers of native plants. Thus, patch size and plant richness should be carefully used for selecting conservation areas because it could result in choosing places threatened by the presence of exotics. Many of the other variables analysed showed no effects on biodiversity at the temporal and geographic scales considered. Ignoring these outcomes could result in choosing sub-optimal areas. We recommend the critical use of general criteria considering the selection process as an opportunity to evaluate the relevance of each criterion at the local level.     

Habitat islands and the equilibrium theory of island biogeography: testing some predictions

Summary Species-area data from a study of marsh birds are used to test five predictions generated by the equilibrium theory of island biogeography. Three predictions are supported: we found a significant species-area relationship, a non-zero level of turnover, and a variance-mean ratio of 0.5. One prediction is rejected: the extinction rates were not greater on small islands. The results of one test are equivocal: the number of species on each island was not always the same. As Gilbert (1980) suggests, a strong species-area relationship alone does not validate the theory. The avian communities we studied were on habitat islands, not true islands, and underwent complete extinction annually. Thus caution must be used before applying the theory to these and other habitat islands.     

The mismeasure of islands: implications for biogeographical theory and the conservation of nature

The focus on place rather than space provides geography with a powerful raison d’être. As in human geography, the functional role of place is integral to the understanding of evolution, persistence and extinction of biotic taxa. This paper re‐examines concepts and biogeographical evidence from a geographical rather than ecological or evolutionary perspective. Functional areography provides convincing arguments for a postmodern deconstruction of major principles of the dynamic Equilibrium Theory of Island Biogeography (ETIB). Endemic oceanic island taxa are functionally insular as a result of long‐term island stability, confinement, isolation, and protection from continental invasion and disturbance. Most continental taxa persist in different, more complex and open spatial systems; their geographical place is therefore fundamentally distinct from the functional insularity of oceanic island taxa. This creates an insular‐continental polarity in biogeography that is currently not reflected in conservation theory. The focus on the biogeographical place leads to the development of the eigenplace concept defined as the functional spatial complex of existence. The application of still popular ETIB concepts in conservation biology is discouraged. The author calls for the integration of functional areography into modern conservation science.     

Metazoan parasites of sticklebacks on Sable Island, Northwest Atlantic Ocean: biogeographic considerations

Three species of sticklebacks ( Apeltes quadracus, Gasterosteus aculeatus , and Pungitius pungitius ( n = 236) were collected from five ponds on Sable Island. The nematodes Pseudoterranova decipiens, Contracaecum sp., Paracuaria adunca , and Cosmucephalus obvelatus , and the cestode Diphyllobothrium ditremum parasitized three-spined sticklebacks ( G. aculeatus ) and four-spined sticklebacks ( A. quadracus ) inhabiting four brackish water ponds. All the parasites except P. decipiens infected nine-spined sticklebacks ( P. pungitius ) from a freshwater pond. In addition, the cestode Schistocephalus pungitii , the copepod Thersitina gasterostei , and the monogenean Gyrodactylus canadensis occurred in nine-spined sticklebacks from the freshwater pond. The two cestodes, the copepod, and the sealworm, P. decipiens , were the most common parasites encountered. The remaining helminths were relatively rare. Most of the parasite species were larval forms which use gulls or seals as definitive hosts. These parasites probably colonized Sable Island with their definitive hosts, whereas only two species ( T. gasterostei and G. canadensis ) successfully colonized the island ponds with their fish hosts. The low parasite species richness encountered is attributed to the impoverished nature of the host fauna of Sable island, and the difficulty of colonization as a result of the island's isolation with respect to the mainland.     

海南岛自然保护区对土壤保持服务功能的保护效果

自然保护区建设是保护生态系统服务的重要手段,在防治土壤侵蚀和维持生态安全方面具有不可替代的作用。以1988年、1998年和2008年3期遥感影像为基础,分析海南保护区对土壤保持功能的长期保护效果,探讨引起保护区土壤保持功能变化的影响因素。结果表明:(1)海南岛保护区内部平均单位面积土壤保持量是1951.59 t hm-2a-1,分别是区外0—5、5—10km和海南岛全省平均水平的2.4、3.2、2.9倍,保护区在土壤保持功能的保育方面发挥着重要作用;(2)在时间尺度上,1988—2008年保护区内外土壤保持功能呈现不同程度的退化趋势,其中保护区外围退化程度显著高于保护区内部(P0.05),后10年的退化程度显著高于前10年(P0.05);(3)从驱动因素上看,1988—2008年经济发展、人口增加和耕地扩张是影响保护区土壤保持功能退化的主要因素,其中在前10年,土壤保持功能与单位面积地区生产总值、单位面积第一产业生产总值、人口密度和耕地比例呈显著负相关(P0.05),而在后10年,土壤保持功能与单位面积地区生产总值、人口密度和耕地比例呈显著负相关(P0.05),由此,应权衡土壤保持功能保护与人为活动的关系,实现生态环境保护与社会经济的协调发展。     

A theory for optimal monitoring of marine reserves

Monitoring of marine reserves has traditionally focused on the task of rejecting the null hypothesis that marine reserves have no impact on the population and community structure of harvested populations. We consider the role of monitoring of marine reserves to gain information needed for management decisions. In particular we use a decision theoretic framework to answer the question: how long should we monitor the recovery of an over‐fished stock to determine the fraction of that stock to reserve? This exposes a natural tension between the cost (in terms of time and money) of additional monitoring, and the benefit of more accurately parameterizing a population model for the stock, that in turn leads to a better decision about the optimal size for the reserve with respect to harvesting. We found that the optimal monitoring time frame is rarely more than 5 years. A higher economic discount rate decreased the optimal monitoring time frame, making the expected benefit of more certainty about parameters in the system negligible compared with the expected gain from earlier exploitation.