Forest fragmentation and the distribution, abundance and conservation of the Tana river red colobus (Procolobus rufomitratus)

Evidence suggests that habitat heterogeneity, disturbance, disease, predation and food resources influence primate population abundance. However, few studies have focused on what habitat factors determine the probability that a primate species will occur in a habitat fragment. We analysed forest habitat and colobus population attributes to determine factors that influenced occurrence and abundance of the critically endangered Tana River red colobus. The probability of colobus inhabiting forests was positively related to the relative amount of habitat edge and canopy tree species composition. Most of the variance in the density of colobus monkeys was explained by basal area of food trees (per ha), basal area per food tree, density of food trees, and basal area per tree for all trees. We conclude that effective conservation of primates in fragmented habitats may require strategies that consider factors that influence both the occurrence of a species and its relative abundance.     

Hunting or habitat degradation? Decline of primate populations in Udzungwa Mountains,Tanzania: An analysis of threats

Hunting and habitat degradation are universal threats to primates across the tropics, thus deciphering the relative impact of threats on population relative abundance is critical to predicting extinction risk and providing conservation recommendations. We studied diurnal primates over a period of nearly 6 years in the Udzungwa Mountains of Tanzania, a site of global importance for primate conservation. We assessed how population relative abundance of five species (of which two are endemic and IUCN-Endangered) differed between two forest blocks that are similar in size and habitat types but contrast strongly in protection level, and how abundance changed during 2004–2009. We also measured habitat and disturbance parameters and, in the unprotected forest, evaluated hunting practices. We found significant differences in primates’ abundance between protected and unprotected forests, with the greater contrast being the lower abundance of colobine monkeys (Udzungwa red colobus and Angolan colobus) in the unprotected forest. At this site moreover, colobines declined to near-extinction over the study period. In contrast, two cercopithecines (Sanje mangabey and Sykes’ monkey) showed slightly higher abundance in the unprotected forest and did not decline significantly. We argue that escalating hunting in the unprotected forest has specifically impacted the canopy-dwelling colobus monkeys, although habitat degradation may also have reduced their abundance. In contrast, cercopithecines did not seem affected by the current hunting, and their greater ecological adaptability may explain the relatively higher abundance in the unprotected forest. We provide recommendations towards the long-term protection of the area.     

Does the matrix matter? A forest primate in a complex agricultural landscape

Many threatened primates now exist in fragmented forest habitats. The survival of these populations may depend on their ability to utilise agricultural or other matrix habitats between forest fragments, but this is poorly known. Here, we systematically investigate an arboreal primate’s use of a heterogeneous matrix in a fragmented forest landscape: the Angola black-and-white colobus (Colobus angolensis palliatus) in southern Kenya. We used a novel technique, based on semi-structured interviews with local informants, to address the difficulty of sampling relatively rare but important events, such as dispersal between fragments. We found that colobus frequently travelled and foraged in indigenous matrix vegetation (such as mangrove, wooded shrubland and shrubland) up to 4 km from the nearest forest fragments. Agricultural habitats, such as perennial plantation (coconut, mango and cashew nut) were also used by colobus for travelling and foraging (in remnant indigenous trees). The probability of sighting colobus in the matrix increased with the proportion of both tall (>6 m) vegetation cover and food tree cover, but declined with distance from forest habitat. Our findings suggest that certain matrix habitats are important for C. a. palliatus, and that future primate conservation initiatives might benefit from adopting a ‘landscape-level’ approach to habitat management, particularly in fragmented forest systems.     

1990-2017年喀斯特自然保护区土地利用变化对生境质量的影响

[目的] 探讨自然保护区生境质量变化规律及其影响因素,为制定有效的区域生态保护政策提供科学依据。[方法] 基于Landsat系列影像数据,采用生境质量估算模型与土地利用转型生境贡献率,以贵州省兴义市坡岗自然保护区为例,分析土地利用变化对不同功能分区生境质量的影响并定量评估退耕还林还草政策情景对生境质量改善效果。[结果] 1990—2017年自然保护区土地流转主要发生在草地和耕地转为林地、其他类型转为草地和林地间。28 a保护区平均生境质量提高15.71%,且呈现先增加后减少的趋势。1990年保护区平均生境质量表现为：缓冲区 > 核心区 > 试验区,2001年以后转换为：核心区 > 缓冲区 > 试验区。在退耕还林还草政策情景下,坡岗自然保护区平均生境质量从当前情景的0.88提高到0.92,生境质量改善。[结论] 坡岗自然保护区的建立、退耕还林还草工程的实施以及人类活动的增加是影响保护区生境质量变化的主要原因。     

The importance of forest area and configuration relative to local habitat factors for conserving forest mammals: A case study of koalas in Queensland, Australia

The loss and fragmentation of forest habitats by human land use are recognised as important factors influencing the decline of forest-dependent fauna. Mammal species that are dependent upon forest habitats are particularly sensitive to habitat loss and fragmentation because they have highly specific habitat requirements, and in many cases have limited ability to move through and utilise the land use matrix. We addressed this problem using a case study of the koala (Phascolarctos cinereus) surveyed in a fragmented rural-urban landscape in southeast Queensland, Australia. We applied a logistic modelling and hierarchical partitioning analysis to determine the importance of forest area and its configuration relative to site (local) and patch-level habitat variables. After taking into account spatial autocorrelation and the year of survey, we found koala occurrence increased with the area of all forest habitats, habitat patch size and the proportion of primary Eucalyptus tree species; and decreased with mean nearest neighbour distance between forest patches, the density of forest patches, and the density of sealed roads. The difference between the effect of habitat area and configuration was not as strong as theory predicts, with the configuration of remnant forest becoming increasingly important as the area of forest habitat declines. We conclude that the area of forest, its configuration across the landscape, as well as the land use matrix, are important determinants of koala occurrence, and that habitat configuration should not be overlooked in the conservation of forest-dependent mammals, such as the koala. We highlight the implications of these findings for koala conservation.     

Designing marine reserves for interacting species: Insights from theory

The primary goals of marine reserves include protecting biodiversity and ecosystem structure. Therefore, a multispecies approach to designing and monitoring reserve networks is necessary. To gain insight into how the interactions between species in marine communities may affect reserve design, we synthesize marine reserve community models and community models with habitat destruction and fragmentation, and we develop new extensions of existing models. This synthesis highlights the potential for species interactions to alter reserve design criteria; in particular, accounting for species interactions often leads to an increase in reserve size necessary to protect populations. Accounting for species interactions also indicates the need to base reserve design and monitoring on a variety of species, especially long-distance dispersers, inferior colonizers, and specialists. Finally, the new model extensions highlight how, given dispersal, source populations outside reserves as well as increases in fished populations after reserve establishment may negatively affect reserve populations of competitors or prey. Therefore, multispecies harvest dynamics outside reserves and before reserve establishment are critical to determining the appropriate reserve size, spacing, and expectations after establishment. These models highlight the importance of species interactions to reserve design and provide guidelines for how this complexity can begin to be incorporated into conservation planning.     

Nowhere to run and nowhere to hide: Response of endemic Mt. Graham red squirrels to catastrophic forest damage

A consequence of isolation is increased susceptibility to catastrophe. Insect damage to fragmented and isolated forests has the potential to serve as a catastrophic force; such damage has increased worldwide due to climate change and fire suppression policies. We examined the response of endangered endemic Mt. Graham red squirrels to catastrophic insect damage due to moths, beetles, and introduced aphids. Insects changed the forest environment significantly for the endemic squirrel by reducing basal area and stem densities of live stems, while increasing number and basal area of standing dead stems. Availability of two major foods, fungi and tree seeds, declined in insect-damaged forests relative to trends in undamaged forests. Numbers of Mt. Graham red squirrels declined precipitously in insect-damaged forests suggesting a catastrophe. Conservation options are limited in such situations. Forest-insect induced catastrophes are likely to become more common in the near future as forest health declines due to past management tactics and climate change. Prudent conservation measures include the anticipation of insect outbreaks and effective forest treatments to decrease likelihood of such catastrophes to species of precarious conservation status, while avoiding abrupt changes to critical habitat.     

Cost-effectiveness of conservation strategies implemented in boreal forests: The area selection process

To protect land from commercial exploitation is a common conservation practice. However, this requires large financial resources and it is therefore important to evaluate the cost-effectiveness of different strategies used in the selection of these conservation areas. In this study we compare four strategies and relate the differences in cost-effectiveness to differences in the selection process. We measure conservation benefits both as the amount of three tree structures and as the number of species in three species groups. We also estimate both the information cost associated with selecting conservation areas and the opportunity cost. We found the key habitat strategy to be the over-all most cost-effective. In this strategy, the areas have a flexible size and are selected by the authorities in a national field survey. The least cost-effective strategy was one where the selection was based only on forest classes in a satellite map. Intermediate were the retention group strategy, where small areas are left by the forest owner at harvesting, and the nature reserve strategy, where large areas are selected by the authorities. We emphasize that the differences we found are associated with the selection process and that other aspects, such as long-term survival of species, may rank the strategies differently. We conclude that the cost-effectiveness of a selection strategy depends on the size of the planning area for selection of conservation areas, the size of the conservation areas, the objective of the agent making the selection, and the amount and type of information on which the selection is based.     

Effect of the landscape context on the density and persistence of a predator population in a protected area subject to environmental variability

Protected areas are the most important tool for the conservation of biodiversity. However, many species are area-demanding and their populations seldom meet their space requirements in reserves. In this context, the unprotected exterior becomes an important part of their home range, and variations in habitat quality of the surroundings of a protected area might affect the dynamics of populations. Using a spatially explicit simulation model, we studied the effect of the surrounding landscape of a protected area on the density and persistence of a predator population inhabiting inside the reserve in different conditions of environmental variability. We simulated individuals of a predator population, their herbivorous prey and a vegetative substrate in a landscape comprised of a square protected area and different types of habitat quality outside the reserve. We studied the combination of three substrate qualities of protected area (inside) with three of the landscape context and three levels of variability of productivity. Our results showed that there were strong effects of both the relative quality of the surrounding landscape and of the environmental variability on the density and persistence of the simulated population inside the protected area. More importantly, we showed that complex patterns emerge when spatial heterogeneity and temporal variability interact with population dynamics. Specifically, under high environmental variability, when the protected area had a high habitat quality, the highest population persistence was not attained when the exterior was also of high quality, but when the surroundings had an intermediate quality. The latter result suggests that, under the mentioned conditions, small enhancements in the quality of the matrix may have, for some species, better effects on increasing persistence in small reserves than large and costly enhancements.     

Small marine reserves can offer long term protection to an endangered fish

The protection of exploited species offered by marine reserves is maximised if individual fish live within the boundaries of the reserve for most of their lives. The direct benefit of this protection, the so called ‘reserve effect’, is the build-up of biomass through an increase in individual numbers and size. This effect can take several years depending on the life history traits of the target species. However, empirical studies on individual fish spatial behaviour at temporal scales long enough to be compatible with that of invoking the reserve effect are still virtually lacking. We studied the inter-annual patterns of habitat use of the dusky grouper (Epinephelusmarginatus), an endangered reef fish predator, using passive acoustic telemetry inside and around a small marine reserve in the Azores, mid-north Atlantic. All 11 individuals resided in the reserve year-round for up to 5 years. During these periods, fish were detected nearly every day and utilised stable core activity areas. Two smaller fish apparently abandoned the area after some time, probably relocating outside the reserve. Our results indicate that even small marine reserves can promote the long-term recovery of some endangered species if the long-term behaviour (i.e. site fidelity) of individuals is appropriate. This result bears direct implications for most existing coastal marine reserves, given that they fall into the small size range and many overexploited reef fish species may be highly site attached.     

Conservation planning with dynamic threats: The role of spatial design and priority setting for species’ persistence

Conservation actions frequently need to be scheduled because both funding and implementation capacity are limited. Two approaches to scheduling are possible. Maximizing gain (MaxGain) which attempts to maximize representation with protected areas, or minimizing loss (MinLoss) which attempts to minimize total loss both inside and outside protected areas. Conservation planners also choose between setting priorities based solely on biodiversity pattern and considering surrogates for biodiversity processes such as connectivity. We address both biodiversity processes and habitat loss in a scheduling framework by comparing four different prioritization strategies defined by MaxGain and MinLoss applied to biodiversity patterns and processes to solve the dynamic area selection problem with variable area cost. We compared each strategy by estimating predicted species’ occurrences within a landscape after 20 years of incremental reservation and loss of habitat. By incorporating species-specific responses to fragmentation, we found that you could improve the performance of conservation strategies. MinLoss was the best approach for conserving both biodiversity pattern and process. However, due to the spatial autocorrelation of habitat loss, reserves selected with this approach tended to become more isolated through time; losing up to 40% of occurrences of edge-sensitive species. Additionally, because of the positive correlation between threats and land cost, reserve networks designed with this approach contained smaller and fewer reserves compared with networks designed with a MaxGain approach. We suggest a possible way to account for the negative effect of fragmentation by considering both local and neighbourhood vulnerability to habitat loss.     

Methods for conservation outside of formal reserve systems: The case of ants in the seasonally dry tropics of Veracruz, Mexico

Like most ecosystems of the world, tropical dry forests of the central coast of the Gulf of Mexico are inadequately preserved. Given that reserve expansion is unlikely, it is imperative that the conservation capacity of the matrix surrounding reserves is enhanced. Here, we examine the habitat value of isolated pasture trees and patches of secondary regrowth in terms of their terrestrial and arboreal ant assemblages in both a wet and dry season. These simplified wooded systems increase species densities within the agricultural matrix and provide habitat for some forest ant species. Estimated species richness of arboreal ants was particularly low on isolated trees, highlighting an important limitation. This was not the case for terrestrial ants, which were particularly species rich under isolated trees. We also found that the inter-site variations in species densities and similarity to the forest ant assemblage for terrestrial and arboreal strata were not correlated, suggesting that responses to restoration may not be as uniform as often thought. This has important implications for the use of indicator taxa in suggesting the response of other taxa. In terms of species composition, neither secondary regrowth nor isolated trees were appropriate replacements for forest fragments, even though the studied forest fragments were small (13-32 ha). The ant assemblages did not exhibit a seasonal change in composition. However, season influenced the contrast between habitats, with isolated trees being more distinct from pasture, and regrowth more closely resembling forests, during the wet season. Microclimatic variables indicate that the forests were least affected by the tropical dry season, and this may contribute to their characteristic fauna. We conclude that even small forest patches make a unique contribution to landscape conservation and that, where reserves are limited, conscientious management of the landscape matrix may provide some species with sufficient new habitat to survive outside of reserve systems. These conclusions are influenced by both season and strata studied.     

Prioritisation of conservation areas in the Western Ghats, India

Areas of high conservation value were identified in the Western Ghats using a systematic conservation planning approach. Surrogates were chosen and assessed for effectiveness on the basis of spatial congruence using Pearson’s correlations and Mantel’s tests. The surrogates were, threatened and endemic plant and vertebrate species, unfragmented forest areas, dry forests, sub-regionally rare vegetation types, and a remotely sensed surrogate for unique evergreen ecosystems. At the scale of this analysis, amphibian richness was most highly correlated with overall threatened and endemic species richness, whereas mammals, especially wide-ranging species, were better at capturing overall animal and habitat diversity. There was a significant relationship between a remote sensing based habitat surrogate and endemic tree diversity and composition. None of the taxa or habitats served as a complete surrogate for the others. Sites were prioritised on the basis of their irreplaceability value using all five surrogates. Two alternative reserve networks are presented, one with minimal representation of surrogates, and the second with 3 occurrences of each species and 25% of each habitat type. These networks cover 8% and 29% of the region respectively. Seventy percent of the completely irreplaceable sites are outside the current protected area network. While the existing protected area network meets the minimal representation target for 88% of the species chosen in this study and all of the habitat surrogates, it is not representative with regard to amphibians, endemic tree species and small mammals. Much of the prioritised unprotected area is under reserve forests and can thus be incorporated into a wider network of conservation areas.     

The effects of including marine ecological values in terrestrial reserve planning for a forest-nesting seabird

Theoretical advances in systematic reserve design aim to promote the efficient use of limited conservation resources and to increase the likelihood that reserve networks enhance the persistence of valued species and ecosystems. However, these methods have rarely been applied to species that rely on spatially disjunct habitats. We used the marbled murrelet, a seabird that requires old-growth forest in which to nest and high quality marine habitats in which to forage, as a case study to explore methods of incorporating multiple ecological values into single species spatial reserve design. Specifically, we used the cost function in MARXAN to include the ecological value of marine habitats while identifying spatial solutions for terrestrial nesting habitat reserves. Including marine values influenced terrestrial reserve designs most when terrestrial habitat targets were low and little or none of the target was represented in pre-existing protected areas. Our results suggest that including marine values in the planning process will influence marbled murrelet terrestrial reserve designs most where substantial terrestrial nesting habitat still exists, where new reserves are relatively unconstrained by pre-existing reserves, or when conservation resources only allow the protection of a small fraction of available habitat. This paper presents a novel framework for incorporating multiple measures of ecological value in the spatial reserve design process and should be particularly useful for species that rely on multiple habitats during their life cycle.     

Responses to marine reserves: Decreased dispersion of the sparid Pagrus auratus (snapper)

Quantifying the movement of exploited species inside marine reserves is a popular research topic, yet few studies have quantified movement inside and outside of reserves. If individuals inside reserves behave differently to those outside, this information should be incorporated into reserve design and in management efforts to avoid the selective removal of certain behaviors. We used acoustic telemetry to monitor the movements of the sparid Pagrus auratus (snapper) inside and outside a marine reserve (the Leigh Marine Reserve, north-eastern New Zealand). We tagged 39 snapper within an array of acoustic receivers that encompassed reserve and fished areas. Nineteen snapper were resident over a 5-month period; the remainder either left the array or died. Residential fish expressed two home range types. One group had uni-modal home ranges that on average encompassed c.900 m linear distance. All nine residential snapper from the reserve displayed this behavior, as well as five of ten residential fish from the non-reserve area. The second group (five fish, all from the non-reserve area) had home ranges with two separate modes (bi-modal home ranges), which on average encompassed c.2 100 m linear distance. We suggest that some aspect of the marine reserve environment encourages extreme residency by either the modification of individual behaviors or through the removal of selective exploitation. If true this suggests that reserves and populations of exploited animals may become dependent on the life history characteristics of the individuals they encourage or select for.     

Habitat selection of endangered and endemic large flying-foxes in Subic Bay, Philippines

Large flying-foxes in insular Southeast Asia are the most threatened of the Old World fruit bats due to high levels of deforestation and hunting and effectively little local conservation commitment. The forest at Subic Bay, Philippines, supports a rare, large colony of vulnerable Philippine giant fruit bats (Pteropus vampyrus lanensis) and endangered and endemic golden-crowned flying-foxes (Acerodon jubatus). These large flying-foxes are optimal for conservation focus, because in addition to being keystone, flagship, and umbrella species, the bats are important to Subic Bay’s economy and its indigenous cultures. Habitat selection information streamlines management’s efforts to protect and conserve these popular but threatened animals. We used radio telemetry to describe the bats’ nighttime use of habitat on two ecological scales: vegetation and microhabitat. The fruit bats used the entire 14,000 ha study area, including all of Subic Bay Watershed Reserve, as well as neighboring forests just outside the protected area boundaries. Their recorded foraging locations ranged between 0.4 and 12 km from the roost. We compared the bats’ use to the availability of vegetative habitat types, riparian areas, and bat trees. The fruit bats’ locations showed a preference for undisturbed forest types and selection against disturbed and agricultural areas. Bat locations also showed selection for particular fruiting/flowering bat trees. The bats showed strong preference for riparian areas; locations were in riparian areas over four times more than expected. From these results we recommend that management focus flying-fox conservation efforts on undisturbed forest and riparian areas.     

The influence of life history attributes and fishing pressure on the efficacy of marine reserves

Two key questions regarding “no-take” marine reserves are: (1) how effective are reserves likely to be, and (2) how does effectiveness vary with life history attributes and the relative size of reserves. To investigate these questions, we use a simple Ricker model that includes fishing, larval dispersal, and larval loss while in a planktonic pool, and that tracks protected and unprotected populations. We applied two different measures of reserve effectiveness to our simulation results. One metric was intended to reflect goals oriented towards conservation and the second was intended to reflect fishery enhancement goals. Both metrics compare the situation before reserves are established to after the reserve has been in place and a new equilibrium was reached. Yield effectiveness is defined as the total equilibrium annual harvest after reserves are established divided by the total annual harvest before reserves are established. Conservation effectiveness is defined as the average adult density inside the reserve divided by the average density in the same area prior to reserve establishment. A substantial fraction of the 5120 simulated parameter combinations representing different harvest rates and life history attributes went extinct in the absence of a reserve, and these scenarios leading to extinction could be predicted accurately (85% aptly classified) simply on the basis of exploitation rate and population growth rate. Of the cases that did not go extinct, we compared the performance of reserves as measured by each effectiveness metric. Few of the cases (less than 8%) produced effective reserves as measured in terms of increased harvest; whereas over half of the cases resulted in effective reserves as measured by conservation effectiveness. Moreover, the two measures of reserve effectiveness were only weakly correlated. Simple linear regression or polynomial regression could explain at most 23% of the variation in reserve effectiveness as measured by either metric. As expected, the size of the reserve area had a marked and typically negative effect on total annual yield, which suggests that while marine protected areas may do a good job of conserving protected populations, there will generally be pressure from the fishing community to keep them small because of their tendency to reduce total catch.     

Marine protected areas export larvae of infauna, but not of bioengineering mussels to adjacent areas

Populations of organisms that create habitat can often be fragmented throughout landscapes by anthropogenic disturbances such as harvesting and loss or change to the identity of such bioengineers may lead to large changes in biodiversity. Using the fauna associated with a bioengineer, the intertidal mussel Perna perna, we tested hypotheses about the relative importance of larval export from protected populations in marine reserves. Harvesting led to the replacement of P. perna and the domination of shores outside reserves by turf-forming coralline algae, mostly Corallina spp. We determined whether the diverse fauna recruiting onto artificial units of habitat placed within mussel beds differed between reserves and non-reserve areas or whether shores outside reserves, and open to harvesting, received recruits through larval export from reserves. Furthermore, we determined whether this was affected by the distance away from reserves and whether colonisation was achieved by movement of adults from surrounding biogenic habitats or via the plankton. Overall, we found no effect of increasing distance away from a reserve on the cover of adult mussels or associated fauna. We found strong effects of the presence of marine reserves on abundances of molluscs and polychaetes but not crustaceans. There were greater densities of molluscs in sites with a reserve (i.e. inside reserves, and up to 5 km outside reserve boundaries), but more polychaetes in exploited sites. For molluscs, this pattern was driven by gastropods rather than bivalves. Furthermore, although reserves had greater cover of adult mussels than non-reserve areas, recruitment of mussels was not greater inside or near to reserves. Our study illustrates the effectiveness of these reserves in protecting stocks of adult mussels, and although there was no evidence that reserves provided export of the larvae of mussels (the target species), they did provide larval export of non-targeted associated species. By protecting a harvested bioengineer and through export of the larvae of its associated fauna, these reserves fulfil some, but not all the conservation aims of a marine protected area.