Single Large Or Several Small Research Articles

Single large AND several small habitat patches: A community perspective on their importance for biodiversity

The debate whether single large or several small (SLOSS) patches benefit biodiversity has existed for decades, but recent literature provides increasing evidence for the importance of small habitats. Possible beneficial mechanisms include reduced presence of predators and competitors in small habitat areas or specific functions such as stepping stones for dispersal. Given the increasing amount of studies highlighting individual behavioral differences that may influence these functions, we hypothesize that the advantage of small versus large habitat patches not only depends on patch functionality but also on the presence of animal personalities (i.e., risk-tolerant vs. risk-averse). Using an individual-based, spatially-explicit community model, we analyzed the diversity of mammal communities in landscapes consisting of a few large habitat islands interspersed with different amounts and sizes of small habitat patches. Within these heterogeneous environments, individuals compete for resources and form home-ranges, with only risk-tolerant individuals using habitat edges. Results show that when risk-tolerant individuals exist, small patches increase species diversity. A strong peak occurs at approximately 20% habitat cover in small patches when those small habitats are only used for foraging but not for breeding and home-range core position. Additional usage as stepping stones for juvenile dispersal further increases species persistence. Overall, our results reveal that a combination of a few large and several small habitat patches promotes biodiversity by enhancing landscape heterogeneity. Here, heterogeneity is created by pronounced differences in habitat functionality, increasing edge density, and variability in habitat use by different behavioral types. The finding that a combination of single large AND several small (SLASS) patches is needed for effective biodiversity preservation has implications for advancing landscape conservation. Particularly in structurally poor agricultural areas, modern technology enables precise management with the opportunity to create small foraging habitats by excluding less profitable agricultural land from cultivation.

SLOSS‐based inferences in a fragmented landscape depend on fragment area and species–area slope

AbstractAimsWhether a Single Large Or Several Small (SLOSS) habitat patches contain more species is central to the debate about how habitat fragmentation threatens species diversity. However, the geographical and biogeographical variables that affect emergent SLOSS patterns remain poorly understood. Here, we quantified SLOSS‐based diversity patterns of woody plant, bird and spider assemblages in a subtropical archipelago of land bridge islands.LocationThousand Island Lake, Zhejiang Province, China.TaxonWoody plants, birds and spiders.MethodsWe analysed species accumulation curves and species–area relationships (SARs) to quantify SLOSS‐based patterns of all, common and rare species for each taxon across different groupings of islands. Differences in the number of species between a single large island and sets of several small islands were measured in these analyses using a Saturation index (SI) and SLOSS index. Generalized additive models were used to assess the relationships between SI and SLOSS index values and the maximum area of islands included in the analysis, the slope of SARs (i.e. z‐score) and the degree of nestedness.ResultsSI values increased with the maximum area of islands for three taxa, while SLOSS index values only increased with the maximum island area for woody plants. SI values increased as z‐scores of woody plants decreased, and showed a quadratic relationship for birds and spiders. SLOSS index values decreased as z‐scores of three taxa increased. The degree of nestedness and SI values or SLOSS index values were weakly correlated with all, rare and common species in the three taxa.Main conclusionsSLOSS‐based inferences of fragmentation effects are contingent on variation in the maximum area of patches included in analyses and the slope of SARs in fragmentated landscapes. Whether conservation efforts should prioritize a single large or several small patches depends on the geographical (e.g. maximum fragment area) and biogeographical (e.g. slope of SAR) attributes of a fragmentated landscape.

Restoring marine ecosystems: Spatial reef configuration triggers taxon‐specific responses among early colonizers

Abstract The longstanding debate in conservation biology on the importance of single large or several small (SLOSS) habitats for preserving biodiversity remains highly relevant, given the ongoing degradation and loss of natural habitats world‐wide. Restoration efforts are often constrained by limited resources, and insights from SLOSS studies therefore have important implications if restoration efforts can be optimized by manipulating the spatial configuration of restored habitats. Yet, the relevance of SLOSS for habitat restoration remains largely unexplored. Here, we report the effects of spatial reef configuration on early colonization of marine organisms after restoring boulder reef habitats. Reefs were restored in single large (SL) and several small (SS) designs in the western Baltic Sea, where century‐long boulder extraction has severely degraded large reef areas and likely exacerbated regional declines in commercially important gadoids (Gadidae spp.). We sampled the field sites using remote underwater video systems in a before‐after control‐impact (BACI) design and obtained probabilistic inferences on restoration and SLOSS effects from Bayesian hierarchical models. Probabilities of a positive restoration effect were high (>95%) for gadoids, labrids and demersal gobies, moderate (60%–75%) for species richness and sand gobies, and low (<5%) for flatfish abundance. Notably, gadoid abundance increased 60‐fold and 129‐fold on average at SL and SS respectively. The species composition at restored reefs deviated from control sites, mainly driven by large‐bodied piscivores. Spatial reef configuration had the strongest effect on small‐bodied mesopredators, including gobies, which were more abundant at SS and driving distinct species assemblages between the reef designs. In addition to providing suitable conditions for reef species, results suggest that SS can also benefit soft‐bottom taxa, possibly through a dispersed predator‐mediated effect relative to SL. Synthesis and applications. This study demonstrates that boulder reef restoration can strongly promote the abundance of exploited gadoids (e.g. Atlantic cod) and is therefore a promising management tool to support top‐down controls by predatory fishes in degraded marine systems. The higher abundance of mesopredators at reefs with a ‘several small’ configuration suggests that the SLOSS dilemma could have long‐term implications for trophic structure and resilience of restored habitats, and should therefore become an important facet within restoration strategies.

Why do several small patches hold more species than few large patches?

AbstractBackgroundThe principle that a single large habitat patch should hold more species than several small patches totalling the same area (SL > SS) is used by conservation agencies to favour protection of large, contiguous areas. Previous reviews of empirical studies have found the opposite, SS > SL, creating the single large or several small (SLOSS) debate.AimsReview the empirical and theoretical SLOSS literature; identify potential mechanisms underlying the SS > SL pattern; evaluate these where possible.LocationGlobal.Time period1976–2018.Major taxaPlants, invertebrates, vertebrates.MethodsLiterature review.ResultsLike previous reviews, I found that SS > SL dominates empirical findings. This pattern remained, although it was somewhat weakened, in studies where sampling intensity was proportional to patch size. I found six classes of theory, and conducted five preliminary evaluations of theory. None of the predictions was supported. The SS > SL pattern held for specialist species groups, suggesting it does not result from incursion by generalists into small patches. I found no evidence for the prediction that the reverse pattern (SL > SS) becomes more common over time since patch creation, through gradual species losses from SS. I found no difference between results for natural and anthropogenic patches. There was also no evidence for predictions that SL > SS is more common when the matrix is more hostile, or for stable than ephemeral patches.Main conclusionsMost empirical comparisons find SS > SL. While there are several potential causes, more empirical work is needed to identify those at play. Meanwhile, conservation practitioners should understand that there is no ecological evidence supporting a general principle to preserve large, contiguous habitat areas rather than multiple small areas of the same total size.

Sustainable Forest Management Tools for the Moscow Region

The paper presents an inventory of current forest formations and a map of forest vegetation in the Moscow region. To assess current forest formations, an approach integrating both ground- and remote sensing data was applied. The transformation of forests in the Moscow region was evaluated by the criteria of changing the quality, quantity and spatial configuration of forests, in accordance with the model SLOSS (Single Large or Several Small). The conceptual model "Pressure-State-Response" (hereinafter PRS) was used to develop appropriate tools for sustainable environmental management in the region. The use of this model made it possible not only to assess the state of forests but also to determine the main impacts affecting them, as well as the effectiveness of measures aimed at optimizing environmental management regimes in order to maintain forest biodiversity. Complex assessment of sets of indicators for each group of PRS criteria is performed for the integrated multicriteria assessment of sustainable forest management within the boundaries of urban districts. The average normalized score was calculated for each group of criteria. Correlation between the scores of the groups of criteria evaluated and classification of administrative units according to the ratio of groups of the K-means method criteria performed. As a result of component-by-component evaluation, the values of indicators are presented in form of tables and map сharts. Benchmarking of Specially Protected Natural Area (SPNA) system and reforestation activities is performed regarding to the forest biodiversity conservation in the urban districts. It is shown that single integrated assessment of the ecological value of the territory (the "State" criterion), an integrated assessment of impact factors (the "Load") and appropriate actions to maintain forest biodiversity (the "Response" criterion) can be considered as an expression of generalized information directly used in decision-making and assessment of current trends for a particular region.

The role of green infrastructures in Italian cities by linking natural and social capital

Urban growth causes numerous threats to human well-being, as a consequence of the loss and degradation of urban and peri-urban green spaces. This research aims to investigate the possible role of green infrastructures (GIs), as providers of ecosystem services, in enhancing urban well-being in the 116 Italian provincial capital cities. The analysis has been based on the conceptual model proposed by the Millennium Ecosystem Assessment (MEA) (2005) to explain how the four categories of ecosystem services (supporting, provisioning, regulating, and cultural) and the components of human well-being are interrelated. In order to perform the assessment, the most suitable indicators of social capital and green infrastructures have been identified from the panel of indices and indicators provided by national official statistics. The corresponding analysis has highlighted that northern Italian cities are characterized by simple but well-managed green infrastructures and wooded areas, with the highest level of social cohesion and inclusion associated with a high value of Gross Domestic Product (GDP) per capita. The southern part of the country is characterized mainly by “Historical greens” and high levels of health and social security but low levels of income, social inclusion and cohesion. This research represents a first attempt to link the different typologies of green infrastructures with the provision of ecosystem services. Given the recognized contribution of GIs in preserving natural habitats in an urban context, the SLOSS (single large or several small) debate, typically applied for conservation purposes, could also be appropriate for GIs. Therefore, it could be necessary to investigate whether fewer large nature preserves (large urban parks), or a patchwork of smaller green areas can better enhance human well-being in an urban context.

Groups of small lakes maintain larger microalgal diversity than large ones

The question of whether one large, continuous area or many smaller habitats maintain more species is one of the most relevant questions in conservation ecology, and it is referred to as the SLOSS (Single Large Or Several Small) dilemma in the literature. This question has not yet been raised in the case of microscopic organisms, therefore we investigated whether or not the SLOSS dilemma could apply to phytoplankton and benthic diatom metacommunities. Benthic diatom and phytoplankton diversity in pools and ponds of different sizes (ranging between 10−2–107 m2) was studied. Species richness of water bodies belonging to neighbouring size categories was compared step by step across the whole size gradient. With the exception of the 104–105 m2 and 105–106 m2 size categories, where phytoplankton and benthic diatom richness values of the SL water bodies were higher than that of the SS ones, findings showed that the diversity of several smaller (SS) sized waters was higher than that in single large water bodies (SL) throughout the whole studied size range. The proportion of the various functional groups of algae, including both the benthic diatoms and phytoplankton, showed remarkable changes from the smaller water bodies to large sized ones.

Single large or several small? Applying biogeographic principles to tree-level conservation and biodiversity offsets

Land development contributes to the clearance of large trees that are sometimes offset with many smaller trees as compensatory wildlife habitat. But are many smaller trees a valid biodiversity offset for the loss of a single large tree? To answer this question, we tested predictions underpinned by island biogeography theory. Targeting birds, we investigated size and landscape context effects at 72 trees of three sizes (small, medium, and large) located in four landscape contexts (reserves, pasture, urban parklands, and urban built-up areas). Significant positive relationships occurred between tree basal area and bird abundance and species richness in all landscape contexts. SLOSS (single large or several small) analysis revealed that in modified landscapes, several small and medium trees supported an equivalent number of individuals and species as a single large tree, but the same pattern was weaker in reserves. Extrapolated rarefaction curves revealed that in reserves and urban built-up areas, many small or medium trees accumulated the same number or more species than large trees. However, in pasture and urban parklands, many small or medium trees accumulated fewer species than large trees. Overall, 29% of bird species were recorded only at large trees, highlighting that many smaller trees will not be suitable habitat compensation for all species. Complementary approaches to biodiversity offsets are needed, balancing large tree preservation and revegetation. Response patterns for birds at trees conformed to some biogeographic predictions (species–area relationship), but not others (habitat–isolation relationship), underscoring the need for novel conceptual frameworks for habitat structures in modified landscapes.

Cost-efficient fenced reserves for conservation: single large or two small?

Fences that exclude alien invasive species are used to reduce predation pressure on reintroduced threatened wildlife. Planning these continuously managed systems of reserves raises an important extension of the Single Large or Several Small (SLOSS) reserve planning framework: the added complexity of ongoing management. We investigate the long-term cost-efficiency of a single large or two small predator exclusion fences in the arid Australian context of reintroducing bilbies Macrotis lagotis, and we highlight the broader significance of our results with sensitivity analysis. A single fence more frequently results in a much larger net cost than two smaller fences. We find that the cost-efficiency of two fences is robust to strong demographic and environmental uncertainty, which can help managers to mitigate the risk of incurring high costs over the entire life of the project.

Stochastic population growth in spatially heterogeneous environments

Classical ecological theory predicts that environmental stochasticity increases extinction risk by reducing the average per-capita growth rate of populations. For sedentary populations in a spatially homogeneous yet temporally variable environment, a simple model of population growth is a stochastic differential equation dZ(t) = μZ(t)dt + σZ(t)dW(t), t ≥ 0, where the conditional law of Z(t+Δt)-Z(t) given Z(t) = z has mean and variance approximately z μΔt and z²σ²Δt when the time increment Δt is small. The long-term stochastic growth rate lim(t→∞) t⁻¹ log Z(t) for such a population equals μ − σ²/2 . Most populations, however, experience spatial as well as temporal variability. To understand the interactive effects of environmental stochasticity, spatial heterogeneity, and dispersal on population growth, we study an analogous model X(t) = (X¹(t) , . . . , X(n)(t)), t ≥ 0, for the population abundances in n patches: the conditional law of X(t+Δt) given X(t) = x is such that the conditional mean of X(i)(t+Δt) − X(i)(t) is approximately [x(i)μ(i) + Σ(j) (x(j) D(ji) − x(i) D(i j) )]Δt where μ(i) is the per capita growth rate in the ith patch and D(ij) is the dispersal rate from the ith patch to the jth patch, and the conditional covariance of X(i)(t+Δt)− X(i)(t) and X(j)(t+Δt) − X(j)(t) is approximately x(i)x(j)σ(ij)Δt for some covariance matrix Σ = (σ(ij)). We show for such a spatially extended population that if S(t) = X¹(t)+· · ·+ X(n)(t) denotes the total population abundance, then Y(t) = X(t)/S(t), the vector of patch proportions, converges in law to a random vector Y(∞) as t → ∞, and the stochastic growth rate lim(t→∞) t⁻¹ log S(t) equals the space-time average per-capita growth rate Σ(i)μ(i)E[Y(i)(∞)] experienced by the population minus half of the space-time average temporal variation E[Σ(i,j) σ(i j)Y(i)(∞) Y(j)(∞)] experienced by the population. Using this characterization of the stochastic growth rate, we derive an explicit expression for the stochastic growth rate for populations living in two patches, determine which choices of the dispersal matrix D produce the maximal stochastic growth rate for a freely dispersing population, derive an analytic approximation of the stochastic growth rate for dispersal limited populations, and use group theoretic techniques to approximate the stochastic growth rate for populations living in multi-scale landscapes (e.g. insects on plants in meadows on islands). Our results provide fundamental insights into "ideal free" movement in the face of uncertainty, the persistence of coupled sink populations, the evolution of dispersal rates, and the single large or several small (SLOSS) debate in conservation biology. For example, our analysis implies that even in the absence of density-dependent feedbacks, ideal-free dispersers occupy multiple patches in spatially heterogeneous environments provided environmental fluctuations are sufficiently strong and sufficiently weakly correlated across space. In contrast, for diffusively dispersing populations living in similar environments, intermediate dispersal rates maximize their stochastic growth rate.

Relative contribution of small mountain ponds to regional richness of littoral macroinvertebrates and the implications for conservation

ABSTRACT Biodiversity is a central concept in conservation programme design. Until recently, ponds were neglected habitats probably owing to their small size and to the ignorance of their real conservation value. The classical theory of species‐area relationship (SAR) might apparently support such a view by predicting low richness values in small habitat patches. SAR theory does not take into account the fact that groups of small habitat patches can significantly contribute to regional richness, regardless of their overall small area. This work intends to contribute to the SLOSS (single large or several small) debate with data on littoral macroinvertebrates from mountain ponds. Do groups of small ponds support communities with higher biodiversity than a single large lake? Littoral macroinvertebrate richness, both local and regional, were measured in 17 ponds and one large lake from Sanabria Natural Park (NW Spain). In order to guarantee valid comparisons among systems, observed and estimated richness, as well as rarefaction methods were used. Although local richness in the lake was much higher than in any single pond, regional richness of ponds widely exceeded the value measured in the lake regardless of their small overall area. Six to seven ponds were enough to obtain an accumulated average richness equivalent to that in the lake. This pattern may be caused partly by increased habitat heterogeneity as proposed by the niche theory. Metacommunity theory might help to explain the high regional richness measured in the group of ponds in the study area. Whatever the explanation, it is evident that groups of mountain ponds strongly contribute to regional richness, a conclusion that should be taken into account by management programmes. There is a gap in this respect in European legislation (the EC Habitats Directive and Water Framework Directive), which fails to include groups of ponds as an additional habitat category. Copyright © 2012 John Wiley & Sons, Ltd.

A multiscale analysis of canopy structure in Fagus sylvatica L. and Quercus cerris L. old‐growth forests in the Cilento and Vallo di Diano National Park

Broadleaved forest is one of the most severely exploited and threatened ecosystems worldwide such that many authors have highlighted the scarcity of undisturbed old‐growth broadleaved forests, especially in southern Europe. From an ecological perspective, old‐growth forests are considered to be significant for their structural diversity and complex ecological relationships among species. In this paper, we compare ground measurements of leaf area index (LAI) and the remotely sensed normalized difference vegetation index (NDVI) autocorrelation pattern of two old‐growth forest stands in the Cilento National Park (southern Italy) with two nearby managed forests stands of the same type. Results show that old‐growth forests have higher fine‐scale variability in both LAI and NDVI values and longer autocorrelation ranges than the corresponding managed forests. The potential relevance of these findings for the single large or several small (SLOSS) debate is also briefly discussed.

都市孤立林の植物種多様性の保全では単一の大面積林と複数の小面積林のどちらが重要か？

The present study was performed to determine whether a single large or several small (SLOSS) forest fragments contain greater numbers of plant species in urban areas. We calculated the cumulative numbers of plant species and total area of 1-5 patch combinations in 22 fragmented forest patches in the Kyoto City area. The number of plant species in several (2-5) small patches tended to be greater than that in single large patches. Combinations of several patches containing more plants had longer perimeters, shorter isolation distances from mountain forests, or more micro landform types. Therefore, in an urban plant conservation strategy, small patches should be created, and such distributions should take into consideration landscape elements, such as perimeter, isolation, and internal habitat diversity.

Economic considerations in the optimal size and number of reserve sites

The debate among ecologists on the optimal number of reserve sites under a fixed maximum total reserve area—the single large or several small (SLOSS) problem—has so far neglected the economic aspects of the problem. This paper argues that economic considerations can affect the optimal number and size of reserve sites and should therefore be taken into consideration in the SLOSS discussion. The paper presents a tractable analytical model to determine the socially optimal number of reserve sites to be allocated in a farming area under a fixed total reserve area, taking the opportunity costs of nature conservation (in this case, agricultural profits) into consideration. Furthermore, the effect of land trade and related transaction costs on the socially optimal number of reserve sites is analyzed. The analysis suggests that in the presence of diminishing returns to farming area, the socially optimal number of reserve sites (which maximizes social welfare) is generally larger than the ecologically optimal number (which maximizes an ecological objective such as population viability). When the opportunity costs of conservation can be offset by land transactions, however, the socially optimal number of reserve sites might be closer to the ecological optimum.

Long-Term Persistence of Species and the SLOSS Problem

The single large or several small (SLOSS) problem has been addressed in a large number of empirical and theoretical studies, but no coherent conclusion has yet been reached. Here I study the SLOSS problem in the context of metapopulation dynamics. I assume that there is a fixed total amount A 0 of habitat available, and I derive formulas for the optimal number n and area A of habitat patches, where n= A 0/ A. I consider optimality in two ways. First, I attempt to maximize the time to metapopulation extinction, which is a relevant measure for metapopulation viability for rare and threatened species. Second, I attempt to maximize the metapopulation capacity of the habitat patch network, which corresponds both with maximizing the distance to the deterministic extinction threshold and with maximizing the fraction of occupied patches. I show that in the typical case, a small number of large patches maximizes the metapopulation capacity, while an intermediate number of habitat patches maximizes the time to extinction. The main conclusion stemming from the analysis is that the optimal number of patches is largely affected by the relationship between habitat patch area and rates of immigration, emigration and local extinction. Here this relationship is summarized by a single factor ζ, termed the patch area scaling factor.

Conservation of vascular plants in single large and several small mires: species richness, rarity and taxonomic diversity

1. This study on vascular plant species of boreal spruce and pine mires concentrated on two geometrical principles: whether single large or several small (SLOSS) reserves contain more species and whether patch shape should be as nearly circular as possible. 2. SLOSS and patch shape have usually been tested by using species richness. Only a few studies have taken the rarity of species into account, and taxonomic diversity has never been used. In our study, all three of these factors were used. 3. Our results showed that the number of species was not related to the spruce mire size, but it increased in relation to the pine mire size. In contrast, the rarity score increased in relation to the area of spruce mires, but it was not related to the area of pine mires. Taxonomic diversity was not related to size in the case of spruce mires, but it increased with pine mires. 4. The SLOSS comparison showed that several small mires contained more vascular plant species than a large one of equal size. Several small mires also had higher rarity scores and taxonomic diversity than a single large mire. The number of species, rarity score and taxonomic diversity increased in relation to the number of small mires in a group. The same results were obtained with both spruce and pine mires. 5. Species richness, rarity score and taxonomic diversity were not related to mire shape. The results did not depend on the mire type.

Breeding bird communities in fragmented wetlands

Abstract The breeding bird communities present in 33 isolated wetlands in the Po plain (northern Italy), ranging in size from 0.3 to 63 ha, were investigated in order to evaluate the effects of area, isolation and habitat diversity on community structure. In simple and multiple regressions, the effect of area was always preponderant (r2 = 64–83%). No other variables affected the number of species nesting exclusively within the wetlands while habitat structural diversity and isolation significantly increased the explained variance of the total number of species and of other community variables. The S.L.O.S.S. (Single Large or Several Small) debate is criticized where species level studies are not carried out.

A Comment on Quinn and Hastings: Extinction in Subdivided Habitats

Conservation BiologyVolume 2, Issue 3 p. 290-292 A Comment on Quinn and Hastings: Extinction in Subdivided Habitats MICHAEL E. GILPIN, MICHAEL E. GILPIN Department of Biology (C-016) University of California at San Diego La Jolla, CA 92093, USA.Search for more papers by this author MICHAEL E. GILPIN, MICHAEL E. GILPIN Department of Biology (C-016) University of California at San Diego La Jolla, CA 92093, USA.Search for more papers by this author First published: September 1988 https://doi.org/10.1111/j.1523-1739.1988.tb00186.xCitations: 34AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume2, Issue3September 1988Pages 290-292 RelatedInformation

What do genetics and ecology tell us about the design of nature reserves?

The SLOSS (single large or several small) debate is no longer an issue in the discussion about the optimal size of nature reserves. The best way to estimate the minimum sizes of reserves may be a three-step process: (1) identify target or keystone species whose disappearance would significantly decrease the value or species diversity of the reserve; (2) determine the minimum number of individuals in a population needed to guarantee a high probability of survival for these species; (3) using known densities, estimate the area needed to sustain the minimum number. The forces that affect population viability and determine MVPs (minimum viable populations) are extremely complex. Thoughtful estimates of MVPs for many animal species are rarely lower than an effective size of a few hundred. Attempts to save only common or smaller species in a community will usually be ill-fated because of the web of ecological relationships between species, including the importance of predation and herbivory in the maintenance of species diversity. Other topics discussed include the complementarity of conservation goals, the problematic function of corridors and the value of buffer zones.

Conservation and Obfuscation: Subdivision of Reserves

Conservation and Obfuscation: Subdivision of Reserves