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.     

The effects of habitat loss, fragmentation, and community homogenization on resilience in estuaries.

When changes in the frequency and extent of disturbance outstrip the recovery potential of resident communities, the selective removal of species contributes to habitat loss and fragmentation across landscapes. The degree to which habitat change is likely to influence community resilience will depend on metacommunity structure and connectivity. Thus ecological connectivity is central to understanding the potential for cumulative effects to impact upon diversity. The importance of these issues to coastal marine communities, where the prevailing concept of open communities composed of highly dispersive species is being challenged, indicates that these systems may be more sensitive to cumulative impacts than previously thought. We conducted a disturbance-recovery experiment across gradients of community type and environmental conditions to assess the roles of ecological connectivity and regional variations in community structure on the recovery of species richness, total abundance, and community composition in Mahurangi Harbour, New Zealand. After 394 days, significant differences in recovery between sites were apparent. Statistical models explaining a high proportion of the variability (R2 > 0.92) suggested that community recovery rates were controlled by a combination of physical and ecological features operating across spatial scales, affecting successional processes. The dynamic and complex interplay of ecological and environmental processes we observed driving patch recovery across the estuarine landscape are integral to recovery from disturbances in heterogeneous environments. This link between succession/recovery, disturbance, and heterogeneity confirms the utility of disturbance-recovery experiments as assays for cumulative change due to fragmentation and habitat change in estuaries.     

Differences in gypsum plant communities associated with habitat fragmentation and livestock grazing.

The negative consequences of habitat fragmentation for plant communities have been documented in many regions of the world. In some fragmented habitats, livestock grazing has been proposed to be a dispersal mechanism reducing isolation between fragments. In others, grazing acts together with fragmentation in a way that increases habitat degradation. Iberian gypsum plant communities have been grazed and fragmented by agricultural practices for centuries. Although their conservation is considered a priority by the European Community, the effects of fragmentation on gypsum plant communities and the possible role of livestock grazing remain unknown. In addition, a substantial proportion of plant species growing in gypsum environments are gypsum specialists. They could be particularly affected by fragmentation, as was found for other habitat specialists (i.e., serpentine and calcareous specialists). In this study (1) we investigated the effect of fragmentation and grazing on gypsum plant community composition (species and life-forms), and (2) we tested to see if gypsum specialists were differently affected by fragmentation and grazing than habitat generalists. A vegetation survey was conducted in the largest gypsum outcrop of Europe (Middle Ebro Valley, northeast Spain). Fragmented and continuous sites in grazed and ungrazed areas were compared. Measurements related to species and composition of life-forms were contrasted first for the whole gypsum plant community and then specifically for the gypsum specialists. In the whole community, our results showed lower plant species diversity in fragmented sites, mainly due to the larger dominance of species more tolerant to fragmented habitat conditions. With livestock grazing, the plant species richness and the similarity in plant species composition between remnants was larger, suggesting that animals were acting as dispersal agents between fragments. As expected, gypsum specialists were less abundant in fragmented areas, and grazing led to the disappearance of the rare gypsum specialist Campanula fastigiata. According to our results, conservation strategies for gypsum plant communities in human-dominated landscapes should consider that fragmentation and grazing modify plant community composition affecting gypsum specialists in particular.     

A multi-scale examination of stopover habitat use by birds

Most of our understanding of habitat use by migrating land birds comes from studies conducted at single, small spatial scales, which may overemphasize the importance of intrinsic habitat factors, such as food availability, in shaping migrant distributions. We believe that a multi-scale approach is essential to assess the influence of factors that control en route habitat use. We determined the relative importance of eight variables, each operating at a habitat-patch, landscape, or regional spatial scale, in explaining the differential use of hardwood forests by Nearctic-Neotropical land birds during migration. We estimated bird densities through transect surveys at sites near the Mississippi coast during spring and autumn migration within landscapes with variable amounts of hardwood forest cover. At a regional scale, migrant density increased with proximity to the coast, which was of moderate importance in explaining bird densities, probably due to constraints imposed on migrants when negotiating the Gulf of Mexico. The amount of hardwood forest cover at a landscape scale was positively correlated with arthropod abundance and had the greatest importance in explaining densities of all migrants, as a group, during spring, and of insectivorous migrants during autumn. Among landscape scales ranging from 500 m to 10 km radius, the densities of migrants were, on average, most strongly and positively related to the amount of hardwood forest cover within a 5 km radius. We suggest that hardwood forest cover at this scale may be an indicator of habitat quality that migrants use as a cue when landing at the end of a migratory flight. At the patch scale, direct measures of arthropod abundance and plant community composition were also important in explaining migrant densities, whereas habitat structure was of little importance. The relative amount of fleshy-fruited trees was positively related and was the most important variable explaining frugivorous migrant density during autumn. Although constraints extrinsic to habitat had a moderate role in explaining migrant distributions, our results are consistent with the view that food availability is the ultimate factor shaping the distributions of birds during stopover.     

Nonlinear responses to food availability shape effects of habitat fragmentation on consumers

Fragmentation of landscapes is a pervasive source of environmental change. Although understanding the effects of fragmentation has occupied ecologists for decades, there remain important gaps in our understanding of the way that fragmentation influences mobile organisms. In particular, there is little tested theory explaining the way that fragmentation shapes interactions between consumers and resources. We propose a simple model that explains why fragmentation may harm consumers even when the total amount of resources on the landscape they use remains unchanged. In particular, we show that nonlinearity in the relationship between resource availability and benefits acquired by consumers from resources can cause a decrease in benefits to consumers when landscapes are subdivided into isolated parts and when the distribution of consumers in fragments is not matched to the distribution of resources. We tested predictions of the model using a laboratory system of cabbage looper (Trichoplusia ni) larvae on artificial landscapes. Consistent with the model's predictions, survivorship of larvae decreased when landscapes with heterogeneous resources were fragmented into isolated parts. However, average mass of surviving larvae did not change in response to fragmentation. With basic knowledge of consumer resource use patterns and landscape structure, our model, supported by our experiment, contributes new understanding of the resource-mediated effects of fragmentation on consumers.     

Effects of habitat fragmentation on the genetic structure and connectivity of the black-lipped pearl oyster Pinctada margaritifera populations in French Polynesia

Habitat destruction leading to increased fragmentation is detrimental to species by reducing population size and genetic diversity and by restraining population connectivity. However, little is known about the effects of naturally fragmented habitats on wild populations, especially when it comes to marine benthic invertebrates with long pelagic larval duration. In this framework, we investigated the connectivity and genetic diversity variation among nine wild populations of the black-lipped pearl oyster, Pinctada margaritifera, throughout French Polynesia using ten microsatellite DNA markers. Despite the naturally fragmented habitat (South Pacific oceanic islands), we found high values of genetic diversity and population admixture, indicating connectivity at small and large spatial scales within sampled sites of the Tuamotu, and between the Society and Tuamotu Archipelagos. In the meantime, habitat geomorphology increased genetic drift in populations occurring in small, closed lagoons. Significant genetic structure not correlated to geographic distance was detected mainly between closed and open lagoons. The Marquesas Islands hosted the most divergent populations, likely a result of vicariance. Our results also highlight that migration patterns among lagoons are not symmetrical. Altogether, the general pattern of gene flow, nonsymmetrical migration rates among populations, absence of isolation by distance and absence of recent extinction events found in our study strongly suggest that P. margaritifera populations of French Polynesia follow an asymmetrical island model of dispersal.     

The role of alarm responses in the formation of mixed-species flocks of heathland birds

Summary Birds of ten species with similar short flight distances from a human intruder associated with stonechats (Saxicola torquata), which have large flight and alarm call distances. The attendants probably took advantage of the domain of safety around the stonechat, produced by the difference in flight distance. Stonechats have no reciprocal advantage, and were not seen to initiate flocks.Flocks were formed with both calling and silent stonechats. Benefits in the latter case probably include early warning of danger, but there may also have been a reduction in vigilance by attendants.The relative flocking activity of attendant species (number of associations observed; percentage of incidents with silent stonechats; rate of warning calls by stonechats joined) was related to the species' average flight distance from an intruder (Fig. 1). Possible explanations are consistent with a correspondence between flocking tendency and the degree of benefit obtained.     

Habitat selection increases the isolating effect of habitat fragmentation on the gopher tortoise

Habitat selection requires choice, which differentiates it from habitat use, and choice, in turn, is dependent upon the responses of organisms to the environmental, social, and other cues that they perceive. Habitat selection by the gopher tortoise (Gopherus polyphemus) was investigated by translocating tortoises and monitoring their movements within two sites in central Florida. The first site supported a stable preponderance of high-quality habitat, and tortoises avoided areas with a dense tree canopy cover caused by fire exclusion. The second site was badly invaded by an introduced weed, and tortoises avoided areas where the weed had formed a dense monoculture. At both sites, individuals appeared to be responding to visual cues to avoid areas that were relatively dark. In landscapes with relatively large amounts of high-quality habitat, this avoidance behavior serves the gopher tortoise well by keeping individuals within the dominant habitat type. In degraded areas, high-quality habitat often becomes increasingly uncommon, and the avoidance behavior exhibited by the tortoises will result in individuals becoming confined to small patches, causing a significant reduction in fitness and hence questioning their long-term survival in such areas. The results from our study show that in order to maintain viable tortoise populations in areas increasingly subjected to human fragmentation and degradation, it is crucial not only to suppress tree canopy cover continually and prevent invasion by exotic weeds, but also to be mindful that the avoidance behavior of the gopher tortoise could prevent individuals from fully occupying a high-quality habitat in response to restoration and management efforts.     

Influence of fish on habitat choice of water birds: a whole system experiment

It is notoriously difficult to study population interactions among highly mobile animals that cannot be meaningfully confined to experimental plots of limited size. For example, migratory water birds are believed to suffer from competition with resident fish populations for shared food resources. While observational evidence in support of this hypothesis is accumulating, replicated experiments addressing this issue at the proper spatial scale are lacking. Here, we report from a replicated whole-system experiment in which we stocked large (0.07 km2), shallow (< or =2.5 m deep), highly eutrophic ponds in the bird protection area "Ismaninger Speichersee mit Fischteichen" with different densities of carp and assessed the responses of water birds and their food resources during summer over several years. In all years, the biomasses of benthic macroinvertebrates, macroalgae, and macrophytes as well as the densities of herbivorous, carnivorous, and omnivorous water birds were reduced in carp ponds compared to fishless ponds. The negative effects of carp on food resources and on the numbers of water birds feeding in carp ponds increased over the season (May-September) and were stronger at high than at low stocking densities of carp. Consequently, differences in resource densities between ponds with and without carp increased, and the ranking of ponds with respect to resource densities became more predictable over the season. These factors may have contributed to a seasonal improvement of the birds' abilities to track resource densities across ponds, as suggested by tight correlations of bird numbers on ponds with resource densities late, but not early, in the season.     

An experimental study of habitat selection by birds in a coffee plantation

Unique components of tropical habitats, such as abundant vascular epiphytes, influence the distribution of species and can contribute to the high diversity of many animal groups in the tropics. However, the role of such features in habitat selection and demography of individual species has not been established. Understanding the mechanisms of habitat selection requires both experimental manipulation of habitat structure and detailed estimation of the behavioral and demographic response of animals, e.g., changes in movement patterns and survival probabilities. Such studies have not been conducted in natural tropical forest, perhaps because of high habitat heterogeneity, high species diversity, and low abundances of potential target species. Agroforestry systems support a less diverse flora, with greater spatial homogeneity which, in turn, harbors lower overall species diversity with greater numerical dominance of common species, than natural forests. Furthermore, agroforestry systems are already extensively managed and lend themselves easily to larger scale habitat manipulations than protected natural forest. Thus, agroforestry systems provide a good model environment for beginning to understand processes underlying habitat selection in tropical forest animals. Here, we use multistate, capture-recapture models to investigate how the experimental removal of epiphytes affected monthly movement and survival probabilities of two resident bird species (Common Bush-Tanager [Chlorospingus ophthalmicus] and Golden-crowned Warbler [Basileuterus culicivorus]) in a Mexican shade coffee plantation. We established two paired plots of epiphyte removal and control. We found that Bush-Tanagers were at least five times more likely to emigrate from plots where epiphytes were removed compared to control plots. Habitat-specific movement patterns were not detected in the warbler. However, unlike the Golden-crowned Warbler, Common Bush-Tanagers depend upon epiphytes for nest sites and (seasonally) for foraging. These dispersal patterns imply that active habitat selection based on the presence or absence of epiphytes occurs in C. ophthalmicus on our study area. Survival rates did not vary with habitat in either species. Interestingly, in both species, survival was higher in the nonbreeding season, when birds were in mixed-species flocks. Movement by Common Bush-Tanagers into areas with epiphytes occurred mostly during the breeding season, when mortality-driven opportunity was greatest.     

Response of predators to loss and fragmentation of prey habitat: a review of theory

Despite extensive empirical research and previous reviews, no clear patterns regarding the effects of habitat loss and fragmentation on predator-prey interactions have emerged. We suggest that this is because empirical researchers do not design their studies to test specific hypotheses arising from the theoretical literature. In fact, theoretical work is almost completely ignored by empirical researchers, perhaps because it may be inaccessible to them. The purpose of this paper is to review theoretical work on the effects of habitat loss and fragmentation on predator-prey interactions. We provide a summary of clear, testable theoretical predictions for empirical researchers. To test one or more of these predictions, an empiricist will need certain information on the predator and prey species of interest. This includes: (1) whether the predator is a specialist on one prey species or feeds on many kinds of prey (omnivore and generalist); (2) whether the predator is restricted to the same habitat type as the focal prey (specialist), can use a variety of habitats but has higher survival in the prey habitat (omnivore), or lives primarily outside of the focal prey's habitat (generalist); (3) whether prey-only patches have lower prey extinction rates than predator-prey patches; and (4) whether the prey emigrate at higher rates from predator-prey patches than from prey-only patches. Empiricists also need to be clear on whether they are testing a prediction about habitat loss or habitat fragmentation and need to conduct empirical studies at spatial scales appropriate for testing the theoretical prediction(s). We suggest that appropriate use of the theoretical predictions in future empirical research will resolve the apparent inconsistencies in the empirical literature on this topic.     

Complex responses within a desert bee guild (Hymenoptera: Apiformes) to urban habitat fragmentation.

Urbanization within the Tucson Basin of Arizona during the past 50+ years has fragmented the original desert scrub into patches of different sizes and ages. These remnant patches and the surrounding desert are dominated by Larrea tridentata (creosote bush), a long-lived shrub whose flowers are visited by > 120 native bee species across its range. Twenty-one of these bee species restrict their pollen foraging to L. tridentata. To evaluate the response of this bee fauna to fragmentation, we compared species incidence and abundance patterns for the bee guild visiting L. tridentata at 59 habitat fragments of known size (0.002-5 ha) and age (up to 70 years), and in adjacent desert. The 62 bee species caught during this study responded to fragmentation heterogeneously and not in direct relation to their abundance or incidence in undisturbed desert. Few species found outside the city were entirely absent from urban fragments. Species of ground-nesting L. tridentata specialists were underrepresented in smaller fragments and less abundant in the smaller and older fragments. In contrast, cavity-nesting bees (including one L. tridentata specialist) were overrepresented in the habitat fragments, probably due to enhanced nesting opportunities available in the urban matrix. Small-bodied bee species were no more likely than larger bodied species to be absent from the smaller fragments. The introduced European honey bee, Apis mellifera, was a minor faunal element at > 90% of the fragments and exerted little if any influence on the response of native bee species to fragmentation. Overall, bee response to urban habitat fragmentation was best predicted by ecological traits associated with nesting and dietary breadth. Had species been treated as individual units in the analyses, or pooled together into one analysis, these response patterns may not have been apparent. Pollination interactions with this floral host are probably not adversely affected in this system because of its longevity and ability to attract diverse pollinators but will demand careful further study to understand.     

Meta-analysis of susceptibility of woody plants to loss of genetic diversity through habitat fragmentation

Shrubs and trees are assumed less likely to lose genetic variation in response to habitat fragmentation because they have certain life-history characteristics such as long lifespans and extensive pollen flow. To test this assumption, we conducted a meta-analysis with data on 97 woody plant species derived from 98 studies of habitat fragmentation. We measured the weighted response of four different measures of population-level genetic diversity to habitat fragmentation with Hedge's d and Spearman rank correlation. We tested whether the genetic response to habitat fragmentation was mediated by life-history traits (longevity, pollination mode, and seed dispersal vector) and study characteristics (genetic marker and plant material used). For both tests of effect size habitat fragmentation was associated with a substantial decrease in expected heterozygosity, number of alleles, and percentage of polymorphic loci, whereas the population inbreeding coefficient was not associated with these measures. The largest proportion of variation among effect sizes was explained by pollination mechanism and by the age of the tissue (progeny or adult) that was genotyped. Our primary finding was that wind-pollinated trees and shrubs appeared to be as likely to lose genetic variation as insect-pollinated species, indicating that severe habitat fragmentation may lead to pollen limitation and limited gene flow. In comparison with results of previous meta-analyses on mainly herbaceous species, we found trees and shrubs were as likely to have negative genetic responses to habitat fragmentation as herbaceous species. We also found that the genetic variation in offspring was generally less than that of adult trees, which is evidence of a genetic extinction debt and probably reflects the genetic diversity of the historical, less-fragmented landscape.     

Extinction debt of forest plants persists for more than a century following habitat fragmentation

Following habitat fragmentation individual habitat patches may lose species over time as they pay off their "extinction debt." Species with relatively low rates of population extinction and colonization ("slow" species) may maintain extinction debts for particularly prolonged periods, but few data are available to test this prediction. We analyzed two unusually detailed data sets on forest plant distributions and land-use history from Lincolnshire, United Kingdom, and Vlaams-Brabant, Belgium, to test for an extinction debt in relation to species-specific extinction and colonization rates. Logistic regression models predicting the presence-absence of 36 plant species were first parameterized using data from Lincolnshire, where forest cover has been relatively low (approximately 5-8%) for the past 1000 years. Consistent with extinction debt theory, for relatively slow species (but not fast species) these models systematically underpredicted levels of patch occupancy in Vlaams-Brabant, where forest cover was reduced from approximately 25% to <10% between 1775 and 1900 (it is presently 6.5%). As a consequence, the ability of the Lincolnshire models to predict patch occupancy in Vlaams-Brabant was worse for slow than for fast species. Thus, more than a century after forest fragmentation reached its current level an extinction debt persists for species with low rates of population turnover.     

Cooperative breeding and immunity: a comparative study of PHA response in African birds

Cooperatively breeding birds might be expected to suffer from higher costs of parasitism than pair-breeding species because of two aspects of their ecology which should facilitate horizontal transmission and possibly select for higher parasite virulence: first, they interact regularly with more individuals than pair-breeding species, and second, these individuals are commonly close relatives that could share similar resistance alleles. This hypothesis predicts that cooperative breeders should invest relatively more in immune defence than closely related species which breed in pairs. I tested this prediction comparatively in African birds by examining the response of the immune system to the mitogenic lectin, phytoahemagglutinin (PHA response) in relation to cooperative breeding. Among 66 species, of which 18 breed cooperatively, PHA response was significantly higher in cooperatively breeding species. This association appeared not to be confounded by body size, clutch size, nest position, coloniality or similarity owing to common phylogenetic descent. These results suggest that cooperatively breeding birds may have been selected to invest more than pair-breeders in defences against parasites. If so, then additional costs of philopatry and helping behaviour might be imposed on breeders, helpers and offspring.     

农药对禽鸟的毒性与评价

测定了甲基异柳磷等四种农药对鹌鹑的急性和蓄积毒性，并作出了安全性评价。结果表明，甲基异柳磷和嘧啶氧磷属高毒级农药，克草胺中毒级，单甲脒低毒级。蓄积试验表明，除嘧啶氧磷为中等蓄积外，其余农药均属轻度蓄积。     

Effects of temperature on testicular cycle of wild birds Black headed munia and Spotted munia

A long term investigation was made on the effects of temperature in the reproduction of tropical wild birds, Black headed munia, Munia malacca and Spotted munia, Lonchura punctulata. In Spotted munia delayed gonadal development as well as regression were observed in 12 degrees C treated group. In 20 degrees C treated birds the testicular volume was significantly less in the month of September and October and was significantly more in November compared to the corresponding control values. In 27 degrees C treated birds delay in testicular development was observed. In Black headed munia delayed gonadal development and regression was observed in 12 degrees C and 20 degrees C treated groups. But maximum gonadal development Delayed regression was also noticed in 20 degrees C group. In 27 degrees C treated group an inhibition of the testicular development was noticed during progressive phase (September). Present findings suggest that neither temperature nor continuous illumination could alter the circannual nature of testicular cycle in spotted munia indicating that temperature acts only as supplementary factor in the reproduction of these two bird models. We further suggest that temperature effects are mediated through changes in thyroxine levels.     

Effects of Economic Downturns on Mortality of Wild African Elephants

Abstract: Declines in economic activity and associated changes in human livelihood strategies can increase threats of species overexploitation. This is exemplified by the effects of economic crises, which often drive intensification of subsistence poaching and greater reliance on natural resources. Whereas development theory links natural resource use to social‐economic conditions, few empirical studies of the effect of economic downturns on wild animal species have been conducted. I assessed the relations between African elephant (Loxodonta africana) mortality and human‐caused wounds in Samburu, Kenya and (1) livestock and maize prices (measures of local economic conditions), (2) change in national and regional gross domestic product (GDP) (measures of macroeconomic conditions), and (3) the normalized difference vegetation index (NDVI) (a correlate of primary productivity). In addition, I analyzed household survey data to determine the attitudes of local people toward protected areas and wild animals in the area. When cattle prices in the pastoralist study region were low, human‐caused wounds to and adult mortality of elephants increased. The NDVI was negatively correlated with juvenile mortality, but not correlated with adult mortality. Changes in Kenyan and East Asian (primary market for ivory) GDP did not explain significant variation in mortality. Increased human wounding of elephants and elephant mortality during periods of low livestock prices (local economic downturns) likely reflect an economically driven increase in ivory poaching. Local but not macroeconomic indices explained significant variation in mortality, likely due to the dominance of the subsistence economy in the study area and its political and economic isolation. My results suggest economic metrics can serve as effective indicators of changes in human use of and resulting effects on natural resources. Such information can help focus management approaches (e.g., antipoaching effort or proffering of alternative occupational opportunities) that address variation in local activities that threaten plant and animal populations.     

Effects of Forest Fragmentation and Habitat Degradation on West African Leaf-Litter Frogs

Abstract:  Habitat degradation alters the dynamics and composition of anuran assemblages in tropical forests. The effects of forest fragmentation on the composition of anuran assemblages are so far poorly known. We studied the joint influence of forest fragmentation and degradation on leaf-litter frogs. We specifically asked whether the processes structuring leaf-litter anuran assemblages in fragmented forests are the same as those in continuous forests. We analyzed anuran assemblages with respect to habitat characteristics, including fragmentation and degradation parameters. In comparison with continuous forests, species richness and diversity were lower and assemblage composition was altered in forest fragments. These changes seemed to be mainly caused by habitat degradation rather than forest fragmentation. Availability of aquatic sites for breeding, vegetation structure (including those variables indicating degradation), and leaf-litter cover had the most influence on the presence of single species. The comparatively small impact of fragmentation on anurans might be due to the location of the study area; it still possessed large tracts of continuous forest. These forest blocks may stabilize the regional rainforest climate and thus weaken the effects of fragmentation .     

Predicting the effects of habitat homogenization on marine biodiversity.

Seafloor habitats throughout the world's oceans are being homogenized by physical disturbance. Even though seafloor sediments are commonly considered to be simple and unstructured ecosystems, the negative impacts of habitat homogenization are widespread because resident organisms create much of their habitat's structure. We combine the insight gained from remote sensing of seafloor habitats with recently developed analytical techniques to estimate species richness and assess the potential for change with habitat homogenization. Using habitat-dependent species-area relationships we show that realistic scenarios of habitat homogenization predict biodiversity losses when biogenic habitats in soft sediments are homogenized. We develop a simple model that highlights the degree to which the reductions in the number of species and functional diversity are related to the distribution across habitats of habitat-specific and generalist species. Our results suggest that, by using habitat-dependent species-area relationships, we can better predict variation in biodiversity across seafloor landscapes and contribute to improved management and conservation.