Effects of recreational disturbance on tidal wetlands: supporting the importance of undisturbed roosting sites for waterbird conservation

In coastal wetlands, the increasing level of disturbance from recreational activities could threaten waterbird populations, which overall are showing decreasing trends. Despite the crucial contribution of waterbirds to biodiversity, empirical studies measuring the effects of disturbance on them remain scarce, especially in terms of the impact upon their roosting sites. We developed an experimental treatment to measure the effects of a pedestrian walking on a site used by overwintering waterbirds in a wetland of international importance. We registered 156 events (88 at high tide) of flushing birds, totaling 4,018 individuals. Each treatment drove the flushing of 1?C5?% of the wintering populations of nearly all species present during high tide. In addition, 1.5?% of the Eurasian curlew wintering population was driven to change site. All the effects were found to be reduced during other tidal periods. Therefore, allowing recreational use in a previously undisturbed area can systematically increase daily energy expenditure of significant percentages of different waterbird populations during high tide, and even cause birds to avoid a site completely. These effects will probably be even worse given that our results were derived only from a disturbance source of low magnitude and frequency. We recommend that, prior to developing recreational areas close to the shoreline, coastal wetland managers should study the habitat use of waterbirds during high tide in relation to total waterbird populations using the wetland.     

Islands at bay: rising seas,eroding islands,and waterbird habitat loss in Chesapeake Bay (USA)

Like many resources in the Chesapeake Bay region of the U.S., many waterbird nesting populations have suffered over the past three to four decades. In this study, historic information for the entire Bay and recent results from the Tangier Sound region were evaluated to illustrate patterns of island erosion and habitat loss for 19 breeding species of waterbirds. Aerial imagery and field data collected in the nesting season were the primary sources of data. From 1993/1994 to 2007/2008, a group of 15 islands in Tangier Sound, Virginia were reduced by 21% in area, as most of their small dunes and associated vegetation and forest cover were lost to increased washovers. Concurrently, nesting American black ducks (Anas rubripes) declined by 66% , wading birds (herons-egrets) by 51%, gulls by 72%, common terns (Sterna hirundo) by 96% and black skimmers (Rynchops niger) by about 70% in this complex. The declines noted at the larger Bay-wide scale suggest that this study area maybe symptomatic of a systemic limitation of nesting habitat for these species. The island losses noted in the Chesapeake have also been noted in other Atlantic U.S. coastal states. Stabilization and/or restoration of at least some of the rapidly eroding islands at key coastal areas are critical to help sustain waterbird communities.     

Community composition of aquatic birds in lakes of Bangalore, India

Observations were made on the occurrence, abundance, richness, and diversity of waterbirds in 15 major lakes in Bangalore city during 2008 - 2009. During the study period 35 species of aquatic birds were recorded. The number of aquatic bird species recorded at various lakes ranged from 23 to 35. The percent abundance of waterbirds recorded in the study lakes ranged from 2.46 to 21.49 and itwas significantly different (p < 0.05). The diversity and species evenness of waterbirds in the lakes ranged from 2.07 to 3.16 and 0.32 to 0.76, respectively. There was a significant difference (p < 0.05) in the diversity and species evenness of waterbirds among different lakes. Species richness of the bird population ranged from 2.89 to 4.01 in the different study lakes and it was not significantly different (p > 0.05). There was a variation in number of waterbird species recorded during summer, monsoon and winter seasons. Of the 35 waterbird species, Bubulcus ibis showed cent percent frequency, whereas less frequently (4.44%) observed species was Anas platyrhynchos. Among various waterbird species, Bubulcus ibis, Fulica atra, Tringa hypoleucos, Motacilla maderaspatensis, Phalacrocorax niger Egretta garzetta, Charadrius dubius, Ardeola grayji, Halcyon smymensis and Motacilla alba were frequently encountered in most of the study lakes.     

Prioritizing urban marine habitats for conservation

Urban coastal wetlands and adjoining coves and embayments can provide habitat for significant numbers of waterbirds, despite being subject to high levels of stressors from human activities. Yet to date little emphasis has been placed on identifying these areas and prioritizing them for conservation. In this study I outline a three-step process to identify and prioritize local sites for conservation using waterbird abundance and diversity and an index of the risk to a site from marine development, and apply it to a series of urban coastal sites in two North Atlantic estuaries located in the northeast US. By combining waterbird abundance and species richness with the risk from marine development I generated a ranked list of sites with the highest listed sites having high bird diversity and low risk from development. From this list individual sites can be prioritized for conservation, and various protection scenarios can be evaluated and compared. For example, 7 of the top 10 ranked sites in Boston Harbor, combined with sites already protected under local, state, or federal statutes, represented over half of the total bird diversity in the Harbor. Similarly, in Narragansett Bay 6 of the top 10 sites when combined with sites already protected represent 48.8% of the Bay’s bird diversity. Formally protecting these sites, all of which are at relatively low risk from marine development, could result in the conservation of considerable waterbird habitat at low economic cost (i.e., from loss of development potential). Other ranking scenarios (by bird diversity alone, or by risk from marine development) were also evaluated and compared to the combined ranking. Identification of sites with high bird diversity and low risk from development could provide important information for local land acquisition groups and planning boards when considering options for the conservation of urban coastal habitats.     

Conserving international coastal habitat networks on migratory waterfowl flyways

Migratory waterfowl depend on habitat networks at local, national and international scales for their survival. Coastal habitats are key areas for many waterfowl. Different species use different biotopes and in different places, so overall many parts of the coastal resource are important. As well as national conservation efforts, waterfowl conservation is increasingly focussed worldwide on collaborative international conservation, catalysed by several measures e.g. the Ramsar Convention, the EC Conservation of Wild Birds Directive, and the Bonn Convention Agreement on the Conservation of African/Eurasian Migratory Waterbirds. Several international conservation plans are under development for single species, but a more effective approach may be to develop plans, for assemblages of migratory birds with similar habitat requirements. All such plans must incorporate future sustainable use of the habitats on which the birds depend. Yet migratory bird and coastal habitat conservation is still often approached separately, despite the two being now closely linked to the development of the Natura 2000 site network in the European Community. Implementing the 1992 EC Habitats Directive requires the selection of coastal habitat sites for designation, set in national and international contexts of resource distribution. International coastal habitat inventories are needed to underpin this process. Combining such inventories with assessment of the flyway habitat requirements of waterfowl species and assemblages offers great potential for identifying international coastal habitat networks that meet the objectives of both habitat and migratory waterfowl conservation.     

广东汕头海岸湿地鸟类群落及其多样性

对广东汕头海岸湿地的鸟类资源进行了调查,共记录鸟类100种,隶属15目31科,其中古北界鸟类43种,东洋界鸟类45种,广布种鸟类12种.区系组成呈南北鸟类混杂分布,鸟类的多样性表现出明显的季节性.该湿地有国家二级重点保护鸟类10种,中日候鸟保护协定名录中的鸟类43种.对5个湿地样区的主要鸟类种类和数量进行了调查,结果反映汕头海岸湿地是水鸟类重要的越冬栖息场,鸟类群落多样性指数以三屿围和六合围两个样区较高,分别为3.2306和3.2283,濠江口的多样性指数较低,为1.981.群落多样性指数的高低主要受物种数量和各物种数量均匀度的影响.本文还提出了对鸟类资源保护和管理的建议.表3参9     

Long-term trend of the waterbird community breeding in a heavily man-modified coastal lagoon: the case of the important bird area “Lagoon of Venice”

The aim of the paper is to examine the temporal and spatial changes observed over a 25-year period in the waterbird community nesting in the largest coastal lagoon around the Mediterranean; to examine driving factors for the observed changes; to address the most urgent conservation actions. Published sources and field surveys made between March and July were used to assess number of breeding pairs of the commonest waterbirds in 1990–1992, 2000–02 and 2012–14. The breeding waterbird community exhibited several changes in its structure, with an overall positive trend; the number of species increased from 14 to 25 and the mean yearly abundance increased from 6155 to 14,008 pairs. The diversity (H′) increased slightly, whereas similarity indices and nMDS ordination both highlighted clear differences between 1990 and 1992 and 2012–2014 communities. The increase in richness and abundance were mostly due to the immigration of birds from nearby wetlands, to the partial recovery of lagoon ecological conditions since the end of the 1980s and to the occurrence of suitable man-made habitats, such as fish farms, dredge islands and a constructed wetland. The fraction of the population nesting at artificial sites and fish farms increased from 50% in 1990–1992 till 80% in 2012–2014, highlighting the importance of artificial breeding sites in costal lagoons. At the opposite natural nesting habitats, such as saltmarshes and beaches are losing importance for breeding waterbirds, thus requiring urgent conservation measures.     

中国西南不同湿地类型水鸟多样性评价

水鸟是反映湿地生态系统健康的指标之一,对不同湿地水鸟多样性进行评价能提出有利于湿地生态系统健康良性发展的湿地管理措施,亦能更好地保护水鸟资源。为缓解近年来中国自然湿地退化和消失的问题,中国政府积极推进实施了大量修复自然湿地和新建人工湿地的工程。然而受限于人力、物力和经费,当前对自然湿地和人工湿地水鸟多样性的系统调查和评价多局限于单一地点或局部区域。因水鸟的分布具有地域性,从地域尺度进行不同湿地类型水鸟多样性评价将更为客观,公众科学数据为区域大尺度数据获取提供了可能。本研究借助中国观鸟记录中心数据,比较了2014年1月至2018年2月中国西南4省(市)自然湿地和人工湿地的水鸟物种多样性和组成相似性;结果共记录到9目19科139种水鸟,其中有94.96%的物种分布于自然湿地,67.63%的物种分布于人工湿地;各类群水鸟在自然湿地中的物种数均高于人工湿地。结果说明自然湿地在水鸟保护中具有重要栖息地功能,人工湿地能为大部分水鸟提供栖息地,但不能完全代替自然湿地。自然湿地中的湖泊湿地、河流湿地和沼泽化草甸以及人工湿地中的水库、城市人工景观水面和娱乐水面是水鸟,特别是受威胁水鸟分布的重要湿地类型;建议政府部门重点对上述湿地亚类进行合理的规划和管理。     

Functional Equivalency between Rice Fields and Seminatural Wetland Habitats

Abstract: Evaluating the potential for anthropogenic habitats to act as surrogates for the natural habitats they replace is a key issue in conservation biology. In California, flooded rice fields are used by numerous aquatic birds during winter. If this habitat functions similarly to more natural wetlands, increased flooding may help replace the extensive wetlands that occurred in the region prior to agricultural development. I tested whether food abundance, perceived predation threat, foraging performance, and the way in which birds allocate their time to different behaviors differed between flooded rice fields and seminatural wetlands for several species of aquatic bird. When appropriate, I also compared flooded and unflooded fields. Invertebrate densities did not differ among habitats. Seminatural wetlands had less rice grain but more seeds from other plants than the two rice habitats. The frequency with which predators passed over a feeding area was lower in flooded fields than in unflooded fields or seminatural wetlands. Most differences in feeding performance and time allocation among habitats were small and statistically insignificant. For some species, feeding efficiency was greater in seminatural wetlands than in flooded fields. Increasing attack rates and the amount of time spent feeding when in flooded fields, however, may allow birds to compensate for reduced efficiency. Multivariate analyses showed that group size, predation threat, time of day, date, and water depth often were associated with behaviors, but that these variables rarely accounted for habitat differences. Flooded fields apparently provide equivalent foraging habitat to seminatural wetlands and, because of reduced predation threat, may be a safer habitat for waterbirds. Thus, if managed appropriately, one of the world's dominant forms of agriculture can provide valuable waterbird habitat.     

The oasis effect: response of birds to exurban development in a southwestern savanna

Ranches are being converted to exurban housing developments in the southwestern United States, with potentially significant but little-studied impacts on biological diversity. We counted birds in grasslands and savannas in southeastern Arizona that were grazed by livestock, embedded in low-density exurban housing developments, or both, or neither. Species richness and bird abundance were higher in exurban neighborhoods than in undeveloped landscapes, independent of livestock grazing. The positive response to development was particularly evident among doves, quail, hummingbirds, aerial insectivores, and some but not all ground-foraging sparrows. Effects of livestock grazing were comparatively minor and mostly involved birds with requirements for tall ground cover or the lack of it. The average rank correlation between counts of individual species and housing density was positive across all transects. However, this relationship disappeared among the exurban transects alone, and bird species richness on the exurban transects was negatively correlated with the number of homes nearby. These results suggest that the positive influence of exurban development on avian abundance and variety was greatest at the lowest housing densities. We attribute the attraction of many birds to exurban development to an oasis effect, in which resources otherwise scarce in arid southwestern environments (shade, nectar, nest sites, and especially water) are relatively abundant around exurban home sites. This finding is consistent with the hypothesis that exurban home sites represented resource supply points inside birds' home ranges otherwise consisting mostly of natural vegetation.     

Impacts of Livestock Grazing and Tree Clearing on Birds of Woodland and Riparian Habitats

Abstract:  We investigated the impact of pastoral management on birds in subtropical grassy eucalypt woodland in southeastern Queensland, Australia, where the patterns of land management have made it possible to disentangle the effects of livestock grazing from those of tree clearing. We recorded changes in bird species composition, density, and relative abundance across two woodland habitat types (riparian and nonriparian) and two levels of clearing (wooded and nonwooded) and three levels of livestock grazing (low, moderate, and high) replicated over space (1000 km²) and time (2001–2002). We predicted that species that depend on understory vegetation would be most negatively affected by livestock grazing. A Bayesian generalized linear model showed that the level of grazing had the greatest effect when trees were present. When trees were absent, the impact of grazing was overshadowed by the effects of a lack of trees. Over 65% of species responded to different levels of grazing, and the abundance of 42% of species varied markedly with habitat and grazing. The most common response to grazing was high species relative abundance under low levels of grazing (28% of species), species absence at high levels of grazing (20%), and an increase in abundance with increasing grazing (18%). Despite having similar bird assemblages, the effect of grazing was stronger in riparian habitat than in adjacent woodland habitat. Our results suggest that any level of commercial livestock grazing is detrimental to some woodland birds, particularly the understory-dependant species, as predicted. Nevertheless, provided trees are not cleared, a rich and abundant bird fauna can coexist with moderate levels of grazing. Habitats with high levels of grazing, on the other hand, resulted in a species-poor bird assemblage dominated by birds that are increasing in abundance nationally .     

Influence of Landscape Scale on Farmland Birds Breeding in Semi-Natural Pastures

Abstract: Little attention has been paid to fragmentation effects on organisms living in open habitats in which species may have high mobility and generalized habitat use. We investigated landscape effects on 23 farmland bird species breeding in 72 semi-natural dry pastures distributed equally among three landscape types (agricultural-dominated, mosaic, and forest-dominated) in southcentral Sweden. There were generally higher local abundances of farmland birds in pastures located in agricultural-dominated and mosaic landscapes than in forest-dominated landscapes. Species feeding on a mixed diet as well as resident species and temperate migrants were most numerous in pastures located in agricultural-dominated landscapes and least numerous in forest-dominated landscapes. While controlling for the effects of local pasture area and vegetation structure, we found that the local abundance of 18 ( 78%) farmland bird species was significantly associated with the composition and structure of the surrounding landscape. The landscape distance that explained the largest part of local variation in abundance varied among species according to the size of their breeding territories or foraging home ranges. Our results suggest that habitat use of farmland birds breeding in pastures is affected both by suitable foraging habitats in the surrounding landscape and by nest sites within local pastures. Despite the generally higher abundances of farmland birds in pastures located in agricultural-dominated landscapes, most species of European and Swedish conservation concern had higher abundance in pastures located in more forested landscapes. Thus, the rapid loss of semi-natural dry pastures in forest-dominated landscapes is a serious threat to the future of these species in Sweden.     

Songbird Use of Gallery Woodlands in Recently Cleared and Older Settled Landscapes of the Selva Lacandona, Chiapas, Mexico

Many regions of Central America have undergone wide-scale habitat change as land has been converted for cultivation or grazing. Clearing for agriculture often leaves a variety of regenerating and remnant patches of wooded vegetation. Of particular importance is arroyo vegetation, or strips of trees or tall shrubs growing along streams. Although it is widely acknowledged that tropical arroyo vegetation supports high densities of birds, as avian habitat it remains poorly studied. We used point counts to study populations of migrant and resident songbirds in the arroyo vegetation of settled areas of the Selva Lacandona adjacent to the Montes Azules Biosphere Reserve of southeastern México. Two study areas were established on lands that had been cleared and settled 20–35 and 10 years previously. Our objectives were to assess the value of arroyo vegetation to the conservation of avian species diversity and abundance in agricultural landscapes and to compare the composition and abundance of songbirds in cleared areas settled at different times over a 35-year period. Arroyo vegetation had a wide diversity of songbird species that, in overall terms, differed little between those landscapes cleared recently and those cleared up to 35 years previously. In both areas we found a high abundance of habitat generalists and a smaller number of forest-dependent species, particularly migrants. Loss of forest specialists occurs rapidly, with little further loss as the arroyos become increasingly isolated. Our data also suggest that birds do not crowd into limited habitat as the surrounding vegetation is eliminated, implying that the overall carrying capacity of the agricultural landscape is greatly enhanced as larger areas of arroyo vegetation are protected. Protection of arroyo vegetation will increase the diversity of birds living in agricultural areas and can be achieved simply by expanding upon land-use practices currently in use.     

Rodent Communities in an Exurbanizing Southwestern Landscape (U.S.A.)

Abstract:  Ranches are being converted to exurban housing developments in the southwestern United States, with potentially significant but little-studied impacts on biological diversity. We captured rodents on 48 traplines in grasslands, mesquite savannas, and oak savannas in southeastern Arizona that were grazed by livestock, embedded in exurban housing developments, grazed and embedded in development, or neither grazed nor embedded in development. Independent of habitat or development, rodent species richness, mean rank abundance, and capture rates of all rodents combined were negatively related to presence of livestock grazing or to its effects on vegetative ground cover. Exurban development had no obvious effects on rodent variety or abundance. Results suggest southwestern exurban developments can sustain a rich assemblage of grassland and savanna rodents if housing densities are low and houses are embedded in a matrix of natural vegetation with little grazing.     

Effects of anthropogenic landscapes on population maintenance of waterbirds

Anthropogenic impacts have reduced natural areas but increased the area of anthropogenic landscapes. There is debate about whether anthropogenic landscapes (e.g., farmlands, orchards, and fish ponds) provide alternatives to natural habitat and under what circumstances. We considered whether anthropogenic landscapes can mitigate population declines for waterbirds. We collected data on population trends and biological traits of 1203 populations of 579 species across the planet. Using Bayesian generalized linear mixed models, we tested whether the ability of a species to use an anthropogenic landscape can predict population trends of waterbird globally and of species of conservation concern. Anthropogenic landscapes benefited population maintenance of common but not less-common species. Conversely, the use of anthropogenic landscapes was associated with population declines for threatened species. Our findings delineate some limitations to the ability of anthropogenic landscapes to mitigate population declines, suggesting that the maintenance of global waterbird populations depends on protecting remaining natural areas and improving the habitat quality in anthropogenic landscapes. Article impact statement: Protecting natural areas and improving the quality of anthropogenic landscapes as habitat are both needed to achieve effective conservation.     

Experimental test of the effects of a non-native invasive species on a wintering shorebird

The abundance of nearly one-quarter of the world's shorebird species is declining. At the same time, the number of non-native species in coastal ecosystems is increasing rapidly. In some cases, non-native species may affect negatively the abundance and diversity of shorebird prey species. We conducted an experimental study of the effects of the introduced European green crab (Carcinus maenas) on prey consumption by wintering Dunlin (Calidris alpina) in a central California estuary. We placed green crabs and Dunlin sequentially in field enclosures and measured changes in density of benthic invertebrate prey (e.g. polychaetes and small clams), Dunlin biomass, and gut contents of both Dunlin and crabs and observed foraging behavior of Dunlin. Green crabs significantly affected Dunlin foraging success through both direct and indirect multitrophic linkages. In enclosures with high densities of green crabs, crab foraging reduced the availability of polychaetes, and Dunlin consumed significantly fewer polychaetes compared with Dunlin in enclosures without crabs. High densities of green crabs were also associated with increased availability of small clams. Dunlin consumed significantly more small clams compared with Dunlin in enclosures without crabs. In our literature survey of studies of effects of non-native invasive species on shorebirds, we found three prior experiments that addressed the effect of non-native invasive species on shorebirds. Results of two of these studies showed positive direct effects of non-native invertebrates on shorebirds, 1 showed negative direct effects of a non-native plant on shorebirds through habitat conversion, and none showed indirect effects of non-native invertebrates. We suggest future management of shorebirds explicitly examine how non-native marine species, particularly invertebrates, directly and indirectly affect shorebirds.     

Effects of Controlled Fire and Livestock Grazing on Bird Communities in East African Savannas

Abstract: In East Africa fire and grazing by wild and domestic ungulates maintain savannas, and pastoralists historically set fires and herded livestock through the use of temporary corrals called bomas. In recent decades traditional pastoral practices have declined, and this may be affecting biodiversity. We investigated the effects of prescribed fires and bomas on savanna bird communities in East Africa during the first and second dry seasons of the year (respectively before and after the rains that mark the onset of breeding for most birds). We compared abundance, richness, and community composition on 9‐ha burned plots, recently abandoned bomas, and control plots in the undisturbed matrix habitat over a 3‐year period. Generally, recently burned areas and abandoned bomas attracted greater densities of birds and had different community assemblages than the surrounding matrix. The effects of disturbances were influenced by interactions between primary productivity, represented by the normalized difference vegetation index, and time. Bird densities were highest and a greater proportion of species was observed on burned plots in the months following the fires. Drought conditions equalized bird densities across treatments within 1 year, and individuals from a greater proportion of species were more commonly observed on abandoned bomas. Yearly fluctuations in abundance were less pronounced on bomas than on burns, which indicate that although fire may benefit birds in the short term, bomas may have a more‐lasting positive effect and provide resources during droughts. Several Palearctic migrants were attracted to burned plots regardless of rainfall, which indicates continued fire suppression may threaten their already‐declining populations. Most notably, the paucity of birds observed on the controls suggests that the current structure of the matrix developed as a result of fire suppression. Traditional pastoralism appears critical to the maintenance of avian diversity in these savannas.     

Territory characteristics and coexistence with heterospecifics in the Dartford warbler <Emphasis Type="Italic">Sylvia undata</Emphasis> across a habitat gradient

The study of successional gradients may help to understand the relative influence of habitat structure and competition on territory characteristics. Here, we evaluate the effects of vegetation cover, conspecific and heterospecific densities, and distance to the nearest neighbor on territory size, shape, and overlap in insectivorous birds. We studied these effects along a gradient of postfire habitat regeneration in which foliage cover and densities of focal species varied several-fold. We delineate 197 territories (minimum convex polygons) of the shrub-dwelling Dartford warbler (Sylvia undata) and 255 of the syntopic Sardinian (Sylvia melanocephala), subalpine (Sylvia cantillans) and melodious (Hippolais polyglotta) warblers at three plots in NE Catalonia (Spain and France) in 1987–2005. After accounting for the effect of the number of locations used to delineate polygons, generalized linear mixed models (GLMM) showed a reduction in territory area of the Dartford warbler as conspecific density increased and distance to nearest neighbor decreased, in accordance with the contender pressure hypothesis for territory size regulation. Heterospecific density was not included in the final model of territory size and the effect of habitat structure was marginal. Territory roundness was positively correlated with its size and with conspecific density, probably in relation to energetic constraints, and negatively with heterospecific density. Territorial exclusion was almost complete among Dartford warblers, whereas interspecific territory overlap was extensive and tended to increase with heterospecific density and with structural diversity along the gradient. Our results support the hypothesis that Mediterranean warbler coexistence derives from ecological segregation and not from interspecific territoriality.     

Short-term and long-term facilitation of goose grazing by livestock in the Dutch Wadden Sea area

We studied the impact of livestock grazing on the distribution ofBranta bernicla bernicla (Dark-bellied Brent goose) in the Dutch Wadden Sea during spring. It was hypothesized that livestock facilitate short-term (within-season) grazing for geese as well as long-term (over years). Therefore we measured grazing pressure by geese in salt marsh and polder areas that were either grazed (spring-grazed) or ungrazed during spring (summer-grazed). Additionally, we carried out a preference experiment with captive geese to test the preference between spring-grazed and summer-grazed polder swards. We furthermore compared patterns of use by geese between long-term ungrazed and grazed salt marshes. In May, there is a difference in grazing pressure by geese between polder pastures that are grazed or ungrazed during spring. In this month, the ungrazed polder pastures are abandoned and the geese shift to either the grazed polder pastures or to the salt marsh. Vegetation in the polder that had been spring-grazed had a lower canopy height and a higher tiller density than summer-grazed vegetation. The captive geese in the preference experiment showed a clear preference for vegetation that had been spring-grazed by sheep over ungrazed vegetation. Goose grazing pressure was negatively correlated to canopy height, both on the polder and on the salt marsh. Within the plant communities dominated byFestuca rubra andPuccinellia maritima, marshes that were intensively grazed by livestock generally had higher grazing pressure by geese than long-term ungrazed or lightly grazed salt marshes.     

Use of an Airborne Lidar System to Model Plant Species Composition and Diversity of Mediterranean Oak Forests

Abstract: Airborne lidar is a remote‐sensing tool of increasing importance in ecological and conservation research due to its ability to characterize three‐dimensional vegetation structure. If different aspects of plant species diversity and composition can be related to vegetation structure, landscape‐level assessments of plant communities may be possible. We examined this possibility for Mediterranean oak forests in southern Portugal, which are rich in biological diversity but also threatened. We compared data from a discrete, first‐and‐last return lidar data set collected for 31 plots of cork oak (Quercus suber) and Algerian oak (Quercus canariensis) forest with field data to test whether lidar can be used to predict the vertical structure of vegetation, diversity of plant species, and community type. Lidar‐ and field‐measured structural data were significantly correlated (up to r= 0.85). Diversity of forest species was significantly associated with lidar‐measured vegetation height (R²= 0.50, p < 0.001). Clustering and ordination of the species data pointed to the presence of 2 main forest classes that could be discriminated with an accuracy of 89% on the basis of lidar data. Lidar can be applied widely for mapping of habitat and assessments of habitat condition (e.g., in support of the European Species and Habitats Directive [92/43/EEC]). However, particular attention needs to be paid to issues of survey design: density of lidar points and geospatial accuracy of ground‐truthing and its timing relative to acquisition of lidar data.