Negative Effects Of Habitat Loss Research Articles

The effect of roads on edge permeability and movement patterns for small mammals: a case study with Montane Akodont

Increased edge density is among the main negative effects of habitat loss and fragmentation. Roads are linear infrastructures that may promote barrier effects due to disturbance and mortality effects. We hypothesized that edges of habitat patches bordered by roads are less permeable than roadless edges. We tested whether edge permeability and avoidance are influenced by the presence of paved and dirt roads bordering habitat patches, relatively to roadless edges. We translocated 55 montane akodonts (Akodon montensis) from the interior of vegetation remnants to their edges, and tracked fine-scale movements using spool-and-line devices. Edges were bordered by dirt roads (n = 12 mice), paved roads (n = 21) or were not bordered by roads (n = 22). We assessed edge permeability by comparing the number of tracks with crossings, and by comparing the empirical data to simulated correlated random walks. We also assessed edge avoidance by comparing the net direction travelled and net displacement from edge. No edge crossings were recorded in roaded edges, whereas 36% of tracks in roadless edges crossed the edge at least once. Simulations indicated a significantly lower permeability of roaded edges, while the observed number of crossings in roadless edges was within the expected range. We found no evidence of higher avoidance of roaded edges, as both net direction travelled and displacement were similar across edge types. Roads decreased edge permeability for the montane akodont. This is likely to increase population isolation among vegetation remnants by reducing the structural connectivity in the already fragmented landscape.

Temporal bird community dynamics are strongly affected by landscape fragmentation in a Central American tropical forest region

Habitat loss and fragmentation are considered the main causes of species extinctions, particularly in tropical ecosystems. The objective of this work was to evaluate the temporal dynamics of tropical bird communities in landscapes with different levels of fragmentation in eastern Guatemala. We evaluated five bird community dynamic parameters for forest specialists and generalists: (1) species extinction, (2) species turnover, (3) number of colonizing species, (4) relative species richness, and (5) a homogeneity index. For each of 24 landscapes, community dynamic parameters were estimated from bird point count data, for the 1998–1999 and 2008–2009 periods, accounting for species’ detection probability. Forest specialists had higher extinction rates and a smaller number of colonizing species in landscapes with higher fragmentation, thus having lower species richness in both time periods. Alternatively, forest generalists elicited a completely different pattern, showing a curvilinear association to forest fragmentation for most parameters. Thus, greater community dynamism for forest generalists was shown in landscapes with intermediate levels of fragmentation. Our study supports general theory regarding the expected negative effects of habitat loss and fragmentation on the temporal dynamics of biotic communities, particularly for forest specialists, providing strong evidence from understudied tropical bird communities.

Renovated Breeding Habitat use in Wild & Captive-bred Populations of an Endangered Desert Pupfish

The Leon Springs pupfish (Cyprinodon bovinus) is an endangered fish endemic to Diamond Y Spring in west Texas. To mitigate the negative effects of habitat loss, Diamond Y Spring was renovated to maintain and provide additional breeding habitat. Monsanto Pool, an extant location where C. bovinus have become extirpated, was also renovated in order to increase breeding habitat. After Monsanto Pool was renovated, captive-bred C. bovinus were reintroduced to this location to both increase the range of this species, and evaluate whether captive release is a viable option. These conservation efforts have led to the unique opportunity to evaluate the efficacy of habitat renovations in wild and captivebred populations of C. bovinus, occurring in natural and renovated breeding habitats at two separate locations. The overarching question asked was, is it better to renovate an unoccupied site and introduce captive-bred individuals, or to expand an occupied site that would allow the current population to grow? Habitat use and spawning in three different breeding areas were compared, and specific ecological factors were measured at each site in order to determine if any coincided with observed C. bovinus location preferences. Wild C. bovinus in the natural breeding habitat spawned more, had more spawns per individual male, and had greater territorial stability than wild or captive-bred C. bovinus in renovated habitats. Differences in social system stability and reproductive success between sites may be due to variation in their ability to adapt to a renovated site as well as the ecological makeup of the habitat.

Atlantic forest bird communities provide different but not fewer functions after habitat loss.

Habitat loss often reduces the number of species as well as functional diversity. Dramatic effects to species composition have also been shown, but changes to functional composition have so far been poorly documented, partly owing to a lack of appropriate indices. We here develop three new community indices (i.e. functional integrity, community integrity of ecological groups and community specialization) to investigate how habitat loss affects the diversity and composition of functional traits and species. We used data from more than 5000 individuals of 137 bird species captured in 57 sites in the Brazilian Atlantic Forest, a highly endangered biodiversity hotspot.Results indicate that habitat loss leads to a decrease in functional integrity while measures of functional diversity remain unchanged or are even positively affected. Changes to functional integrity were caused by (i) a decrease in the provisioning of some functions, and an increase in others; (ii) strong within-guild species turnover; and (iii) a replacement of specialists by generalists. Hence, communities from more deforested sites seem to provide different but not fewer functions. We show the importance of investigating changes to both diversity and composition of functional traits and species, as the effects of habitat loss on ecosystem functioning may be more complex than previously thought. Crucially, when only functional diversity is assessed, important changes to ecological functions may remain undetected and negative effects of habitat loss underestimated, thereby imperiling the application of effective conservation actions.

Flowering phenology and nesting resources influence pollinator community composition in a fragmented ecosystem

Introduction Habitat loss is the leading cause of extinctions on the planet. However, negative effects of habitat loss and fragmentation on biodiversity can be reduced if resources in urban or semi-natural areas in the surrounding matrix can be used by wildlife.

Designing for conservation outcomes: the value of remnant habitat for reptiles on ski runs in subalpine landscapes

Subalpine ecosystems are centres of endemism that are important for biodiversity. However, these areas are under threat from the creation, expansion and continued modification of ski runs, activities that have largely negative effects on wildlife. Despite this threat, research on the impacts of ski runs is limited for reptiles—particularly regarding the value of remnant vegetation retained on ski runs. Here we quantify the effects of habitat loss and fragmentation (i.e., patch size, patch isolation and edge effects) on the abundance of a common subalpine lizard and on thermal regimes (a key determinant of lizard distribution) in an Australian ski resort. The number of lizards observed differed significantly with habitat type (ski runs vs. forested areas) and patch isolation, but not patch size. In addition, the edges of patches supported more lizards than any other habitat type. These patterns of lizard distribution can be explained, in part, by the differing thermal regimes in each habitat. Ski runs had significantly higher ground surface temperatures than any other habitat type, precluding their use for a considerable proportion of the activity period of a lizard. In comparison, edges were characterised by lower temperatures than ski runs, but higher temperatures than the core of forested areas, potentially providing a favourable environment for thermoregulation. Based on our results, we conclude that although modified ski runs have a negative effect on lizards, patches of remnant vegetation retained on ski runs are of value for reptiles and their conservation could help mitigate the negative effects of habitat loss caused by ski run creation.

Costing conservation: an expert appraisal of the pollinator habitat benefits of England's entry level stewardship.

Pollination services provided by insects play a key role in English crop production and wider ecology. Despite growing evidence of the negative effects of habitat loss on pollinator populations, limited policy support is available to reverse this pressure. One measure that may provide beneficial habitat to pollinators is England’s entry level stewardship agri-environment scheme. This study uses a novel expert survey to develop weights for a range of models which adjust the balance of Entry Level Stewardship options within the current area of spending. The annual costs of establishing and maintaining these option compositions were estimated at £59.3–£12.4 M above current expenditure. Although this produced substantial reduction in private cost:benefit ratios, the benefits of the scheme to pollinator habitat rose by 7–140 %; significantly increasing the public cost:benefit ratio. This study demonstrates that the scheme has significant untapped potential to provide good quality habitat for pollinators across England, even within existing expenditure. The findings should open debate on the costs and benefits of specific entry level stewardship management options and how these can be enhanced to benefit both participants and biodiversity more equitably.

Interactions between climate and habitat loss effects on biodiversity: a systematic review and meta‐analysis

AbstractClimate change and habitat loss are both key threatening processes driving the global loss in biodiversity. Yet little is known about their synergistic effects on biological populations due to the complexity underlying both processes. If the combined effects of habitat loss and climate change are greater than the effects of each threat individually, current conservation management strategies may be inefficient and at worst ineffective. Therefore, there is a pressing need to identify whether interacting effects between climate change and habitat loss exist and, if so, quantify the magnitude of their impact. In this article, we present a meta‐analysis of studies that quantify the effect of habitat loss on biological populations and examine whether the magnitude of these effects depends on current climatic conditions and historical rates of climate change. We examined 1319 papers on habitat loss and fragmentation, identified from the past 20 years, representing a range of taxa, landscapes, land‐uses, geographic locations and climatic conditions. We find that current climate and climate change are important factors determining the negative effects of habitat loss on species density and/or diversity. The most important determinant of habitat loss and fragmentation effects, averaged across species and geographic regions, was current maximum temperature, with mean precipitation change over the last 100 years of secondary importance. Habitat loss and fragmentation effects were greatest in areas with high maximum temperatures. Conversely, they were lowest in areas where average rainfall has increased over time. To our knowledge, this is the first study to conduct a global terrestrial analysis of existing data to quantify and test for interacting effects between current climate, climatic change and habitat loss on biological populations. Understanding the synergistic effects between climate change and other threatening processes has critical implications for our ability to support and incorporate climate change adaptation measures into policy development and management response.

Negative Effects of Habitat Loss on Survival of Migrant Warblers in a Forest Mosaic

Habitat loss and fragmentation in forested landscapes often negatively affect animal abundance; however, whether these factors also affect fitness is not well known. We hypothesized that observed decreases in bird occurrence and abundance in landscapes with harvested forests are associated with reduced apparent survival of adults. We defined apparent survival as an estimate of survival that accounts for an imperfect resighting probability, but not permanent emigration (i.e., dispersal). We examined the association between spatially extensive habitat loss and apparent survival of males of 2 Neotropical migrant species, Blackburnian Warbler (Dendroica fusca) and Black-Throated Green Warbler (D. virens), over 7 years in the Greater Fundy Ecosystem, New Brunswick, Canada. We estimated apparent survival among and within breeding seasons. We quantified amount of habitat in the context of individual species. In this landscape, boundaries between land-cover types are gradual rather than clearly identifiable and abrupt. Estimated apparent within-season survival of both species decreased as a function of amount of habitat within a 2000-m radius; survival was approximately 12 times (95% CI 3.43-14) greater in landscapes with 85% habitat than in landscapes with 10% habitat. Apparent annual survival also decreased as a function of amount of habitat within a 100-m radius. Over the range of habitat amount, apparent annual survival decreased 15% (95% CI 7-29%) as the amount of habitat decreased. Our results suggest that reduced species occurrence in landscapes with low proportions of habitat is due partly to lower apparent survival at these sites. This mechanism operates both directly (i.e., via effects on mortality or dispersal during breeding) and possibly through indirect effects during the nonbreeding season. Habitat loss was associated not only with a lower number of individuals, but also with lower survival of those individuals.

Contrasting effects of habitat loss and fragmentation on coral-associated reef fishes

Disturbance can result in the fragmentation and/or loss of suitable habitat, both of which can have important consequences for survival, species interactions, and resulting patterns of local diversity. However, effects of habitat loss and fragmentation are typically confounded during disturbance events, and previous attempts to determine their relative significance have proved ineffective. Here we experimentally manipulated live coral habitats to examine the potential independent and interactive effects of habitat loss and fragmentation on survival, abundance, and species richness of recruitment-stage, coral-associated reef fishes. Loss of 75% of live coral from experimental reefs resulted in low survival of a coral-associated damselfish and low abundance and richness of other recruits 16 weeks after habitat manipulations. In contrast, fragmentation had positive effects on damselfish survival and resulted in greater abundance and species richness of other recruits. We hypothesize that spacing of habitat through fragmentation weakens competition within and among species. Comparison of effect sizes over the course of the study period revealed that, in the first six weeks following habitat manipulations, the positive effects of fragmentation were at least four times stronger than the effects of habitat loss. This initial positive effect of fragmentation attenuated considerably after 16 weeks, whereas the negative effects of habitat loss increased in strength over time. There was little indication that the amount of habitat influenced the magnitude of the habitat fragmentation effect. Numerous studies have reported dramatic declines in coral reef fish abundance and diversity in response to disturbances that cause the loss and fragmentation of coral habitats. Our results suggest that these declines occur as a result of habitat loss, not habitat fragmentation. Positive fragmentation effects may actually buffer against the negative effects of habitat loss and contribute to the resistance of reef fish populations to declines in coral cover.

Effects of habitat loss, habitat fragmentation, and isolation on the density, species richness, and distribution of ladybeetles in manipulated alfalfa landscapes

Abstract 1. Habitat loss and fragmentation are the main causes of changes in the distribution and abundance of organisms, and are usually considered to negatively affect the abundance and species richness of organisms in a landscape. Nevertheless, habitat loss and fragmentation have often been confused, and the reported negative effects may only be the result of habitat loss alone, with habitat fragmentation having nil or even positive effects on abundance and species richness.2. Manipulated alfalfa micro‐landscapes and coccinellids (Coleoptera: Coccinellidae) are used to test the effects habitat loss (0% or 84%), fragmentation (4 or 16 fragments), and isolation (2 or 6 m between fragments) on the density, species richness, and distribution of native and exotic species of coccinellids.3. Generally, when considering only the individuals in the remaining fragments, habitat loss had variable effects while habitat fragmentation had a positive effect on the density of two species of coccinellids and on species richness, but did not affect two other species. Isolation usually had no effect. When individuals in the whole landscape were considered, negative effects of habitat loss became apparent for most species, but the positive effects of fragmentation remained only for one species.4. Native and exotic species of coccinellids did not segregate in the different landscapes, and strong positive associations were found most often in landscapes with higher fragmentation and isolation.5. The opposing effects of habitat loss and fragmentation may result in a nil global effect; therefore it is important to separate their effects when studying populations in fragmented landscapes.

Landscape Equivalency Analysis: Methodology for Estimating Spatially Explicit Biodiversity Credits

We propose a biodiversity credit system for trading endangered species habitat designed to minimize and reverse the negative effects of habitat loss and fragmentation, the leading cause of species endangerment in the United States. Given the increasing demand for land, approaches that explicitly balance economic goals against conservation goals are required. The Endangered Species Act balances these conflicts based on the cost to replace habitat. Conservation banking is a means to manage this balance, and we argue for its use to mitigate the effects of habitat fragmentation. Mitigating the effects of land development on biodiversity requires decisions that recognize regional ecological effects resulting from local economic decisions. We propose Landscape Equivalency Analysis (LEA), a landscape-scale approach similar to HEA, as an accounting system to calculate conservation banking credits so that habitat trades do not exacerbate regional ecological effects of local decisions. Credits purchased by public agencies or NGOs for purposes other than mitigating a take create a net investment in natural capital leading to habitat defragmentation. Credits calculated by LEA use metapopulation genetic theory to estimate sustainability criteria against which all trades are judged. The approach is rooted in well-accepted ecological, evolutionary, and economic theory, which helps compensate for the degree of uncertainty regarding the effects of habitat loss and fragmentation on endangered species. LEA requires application of greater scientific rigor than typically applied to endangered species management on private lands but provides an objective, conceptually sound basis for achieving the often conflicting goals of economic efficiency and long-term ecological sustainability.

Dispersal success on spatially structured landscapes: when do spatial pattern and dispersal behavior really matter?

Dispersal is a fundamental component of many spatial population models. Concerns over the need to incorporate detailed information on dispersal behavior in spatially explicit population models (SEPMs) motivated us to undertake a simulation study in which we explored (1) the conditions under which landscape structure affects dispersal success and (2) the dependency of dispersal success on the choice of dispersal algorithm. We simulated individual dispersal as a random process (the mean-field approximation), a percolation process (PD) or a nearest-neighbor process (NND) on random and fractal neutral landscapes across gradients of habitat fragmentation and abundance (0.1–90%). Both landscape structure and dispersal behavior affected dispersal success in landscapes with <30–40% habitat. Landscape structure, in the form of contagious habitat, was always important for predicting the success of weak dispersers constrained to move within a local neighborhood, unless habitat was abundant (≥80%). Dispersers generally attained highest success on landscapes in which habitat had high spatial contagion. Habitat clumping may thus mitigate the negative effects of habitat loss on dispersal success. Spatial pattern is generally not important for predicting dispersal success when habitat abundance exceeds 40% and the mean-field approximation (random dispersal) adequately describes dispersal success in these landscapes. Because species of conservation concern generally occur in landscapes with <20% habitat, modeling dispersal as a random process may not be warranted for these species. In these cases, the required interaction between spatial structure and dispersal may be captured adequately by a simple local dispersal algorithm such that detailed movement rules may not be needed.