Implications of forest utilisation on bird conservation

Waiyaki, E. & Bennun, L.A. 2000. The avifauna of coastal forests in southern Kenya: status and conservation. Ostrich 71 (1 & 2): 247–256.

The biological importance and uniqueness of East African coastal forests is widely recognised; they form an Endemic Bird Area. Important remnants of this fragmented habitat OCCUT on the southern Kenyan coast, but their avifauna has been little studied. In October 1992, September 1993 and May-August 1994, we systematically assessed the avifauna of fifteen South Coast forest fragments (and the threats facing them) using mist-netting, timed species counts and direct observations. Sixty forest-dependent bird species were recorded, amongst them three that are globally threatened (Sokoke Pipit Anthus sokolcensis, Spotted Ground Thrush Turdus fischeri, East Coast Akalat Sheppardia gunningi) three that are near-threatened (Southern Banded Snake Eagle Circaetus fasciolatus, Fischer's Turaco Tauraco fischeri, Plain-backed Sunbird Anthrepres reichenowi) and four that are ‘restricted-range’ (Fischer's Turaco, Sokoke Pipit, Mombasa Woodpecker Campethera mombassica, Uluguru Violet-backed Sunbird Anthreptes neglectus). Globally or regionally threatened and near-threatened species were relatively rare and were patchily distributed across forests. In contrast, most other forest species were widely distributed, being present in most or all fragments. The breakdown of traditional conservation systems, selective logging, encroachment by cultivation and fire-maintained grassland, fragmentation, allocation of land for urban development, pole cutting, charcoal burning, hunting and trapping, prospective mining, bark stripping and elephant damage are the major threats to the continued survival of these forests. Shimba Hills (Mkongani & Longomagandi), Gandini, Mrima, Marenji, Dzombo, Waa, Buda and Gongoni forests met the criteria for Globally Important Bird Areas set by Birdlife International. A number of urgent steps are needed for improved forest management if these important sites are to survive and retain their biological diversity.     

Assessing the conservation value of a human-dominated island landscape: Plant diversity in Hawaii

The conversion of native habitats to pasture and other working lands, unbuilt lands modified by humans for production, is one of the greatest threats to biodiversity. While some human-dominated landscapes on continents support relatively high native biodiversity, this capacity is little studied in oceanic island systems characterized by high endemism and vulnerability to invasion. Using Hawaii as a case study, we assessed the conservation value of working landscapes on an oceanic island by surveying native and non-native plant diversity in mature native forest and in the three dominant land covers/uses to which it has been converted: native, Acacia koa timber plantations, wooded pasture, and open pasture. As expected, native plant diversity (richness and abundance) was significantly higher and non-native abundance significantly lower in mature native forests than any other site type. A. koa plantations and wooded pasture supported four and three times greater, respectively, species richness of native understory plants than open pasture. Also, A. koa plantations and wooded pasture supported similar species communities with about 75% species in common. Conservation and restoration of mature native forest in Hawaii is essential for the protection of native, rare species and limiting the spread of non-native species. A. koa plantations and wooded pasture, however, may help harmonize production and conservation by supporting livelihoods, more biodiversity than open pasture, and some connectivity between native forest remnants important for sustaining landscape-level conservation value into the future.     

The effects of grazing on local colonisation and extinction during early succession

Estimates of colonisation of plant species were made at three spatial scales in an old-field on limestone subject to five experimental sheep grazing regimes. Local extinctions within grazing treatments were estimated in 1-m² permanent quadrats. These data were used to assess the effects of grazing treatment and spatial scale on the process of species change over a period of six years. Colonisation of the lOha field was virtually a random draw of plant species from adj acent vegetation, irrespective of plant life-history traits including dispersal strategy. The effects of grazing on colonisation increased at smaller spatial scales. Colonisation rates changed little during the study on the 10 ha scale, but declined steeply with time at smaller scales. Colonisation rates of short-lived species declined more than those of perennials, and short-lived species were subject to erratic episodes of extinction which did not affect perennials. Short periods of grazing enhanced colonisation rates of all species, but extinction rates were the same as in ungrazed controls. Grazing for longer periods further enhanced colonisation rates, but also increased extinction rates. This produced diversity patterns consistent with a ‘hump-backed model’, except that no grazing treatment was heavy enough to decrease diversity. Ungrazed controls had low species diversity, but areas grazed for longer periods were no more diverse after six years than those grazed for short periods.     

The effects of cattle grazing on plant-pollinator communities in a fragmented Mediterranean landscape

The main aims of this study were to assess grazing impacts on bee communities in fragmented mediterranean shrubland (phrygana) and woodland habitats that also experience frequent wildfires, and to explain the mechanisms by which these impacts occur. Fieldwork was carried out in 1999 and 2000 on Mount Carmel, in northern Israel, a known hot-spot for bee diversity. Habitats with a range of post-burn ages and varying intensities of cattle grazing were surveyed by transect recording, grazing levels, and the diversity and abundance of both flowers and bees were measured. The species richness of both bees and flowers were highest at moderate to high grazing intensities, and path-analysis indicated that the effects of both grazing and fire on bee diversity were mediated mainly through changes in flower diversity, herb flowers being more important than shrubs. The abundance of bees increased with intensified grazing pressure even at the highest levels surveyed. Surprisingly though, changes in bee abundance at high grazing levels were not caused directly by changes in flower cover. The variation in bee abundance may have been due to higher numbers of solitary bees from the family Halictidae in grazed sites, where compacted ground (nesting resource) and composites (forage resource) were abundant. The effects of grazing on plants were clearest in the intermediate-aged sites, where cattle inhibited the growth of some of the dominant shrubs, creating or maintaining more open patches where light-demanding herbs could grow, thus allowing a diverse flora to develop. Overall, bee communities benefit from a relatively high level of grazing in phrygana. Although bee and flower diversity may decrease under very heavy grazing, the present levels of grazing on Mount Carmel appear to have only beneficial effects on the bee community.     

Lizard diversity and agricultural disturbance in a Caribbean forest landscape

Understanding the impact of agriculture on biodiversity is critical for effective conservation management. Our goal was to determine the impact of agricultural disturbance on the lizard fauna of Los Haitises National Park and the surrounding region in the Dominican Republic. This region has a history of extensive agricultural disturbance followed by abrupt abandonment. Abundance and diversity were surveyed in six habitats: relatively undisturbed hilltop (mogote), four habitats disturbed by agriculture (pasture, oil palm plantation, cacao plantation, conuco or home garden), and one forested habitat. Three of these habitats (pasture, cacao plantation, conuco) were also examined at different stages of activity or abandonment. Glue-trap grids were used to sample each habitat. In general, species richness was lower in more heavily or recently disturbed habitats. Richness was lowest in active agricultural habitats where only 54% of the region's lizard species were detected. Notably, agricultural systems differed considerably in their ability to support a diverse lizard assemblage. Abandoned agricultural habitats had slightly higher richness than their active counterparts, but still contained only 69% of the region's species. By contrast, nearly every native species, including several never observed in agriculturally disturbed habitats, were detected on the undisturbed hilltops (mogotes). These mogotes may have served as refugees for species that could not tolerate disturbance when the region was being heavily exploited for agriculture. Overall, our results suggest that the continued protection of the park, and its mogotes in particular, will be required to maintain the region's lizard diversity.     

森林采伐对森林景观的长期影响模拟

应用空间直观景观模型(LANDIS),模拟了小兴安岭友好林业局在有无采伐方案下400年内森林景观的动态变化,并利用统计软件APACK计算代表性树种的分布面积、年龄级和反映物种分布格局的聚集度指数.结果表明:与无采伐相反,采伐下的火干扰模式为高频率小面积低强度火烧;采伐对各种群的分布面积影响不大,但显著改变了种群的年龄结构,主要表现为降低了过熟林的分布面积,而增加了其他年龄级森林的分布面积;采伐降低了各树种的聚集度,导致森林景观一定程度上的破碎化.     

The interactive effects of grazing ungulates and aboveground production on grassland diversity

The variable and nonlinear relationships between plant species richness (SR) and aboveground production (NAP) among terrestrial ecosystems indicate that the energetic capacity of ecosystems interacts with other environmental factors to control diversity. One contributing factor determining plant diversity is herbivory; but few studies have effectively examined the interaction of herbivores and NAP on SR. The objective of this study was to investigate how NAP and herds of native migrating ungulates determine plant SR in grasslands of Yellowstone National Park. Plant SR at peak aboveground biomass was compared inside and outside ungulate exclosures at two spatial scales, 1.0 m² (“local”) and 100 m² (“community”), in ten variable grasslands. NAP also was determined inside and outside exclosures. The relationship between SR and NAP was unimodal for grazed and ungrazed grassland at both spatial scales. Grazers increased local SR, independent of NAP. In contrast, herbivore effects on community SR ranged from no effect among low-productive grassland to an increasingly positive influence as NAP increased. In addition, ungulates reduced beta diversity (the contribution to community SR attributed to variability among local patches) at dry, low-productive and wet, high-productive sites. These results suggest that the size of the pool of species available to colonize grassland is an important factor controlling the response of grassland SR to herbivory, particularly from low- to intermediate-productive grassland.     

Linking vegetation structure and bird organization: response of mixed-species bird flocks to forest succession in subtropical China

As forests undergo natural succession following artificial afforestation, their bird assemblages also change. However, interspecific avian social organization associated with forest succession has not been fully understood, particularly for mixed-species bird flocks. To disentangle how mixed-species flocks change as a function of local forest structure, we analyzed flock characteristics (particularly species richness, flocking frequency and propensity) and vegetation physiognomies along a presumed successional series (early, middle, and advanced) simultaneously in subtropical forests in southern China. As hypothesized, monthly point counts demonstrated that complexity of flocks increases with the progression of natural forest succession at a local scale. Advanced forests differed significantly from pioneering plantations with respect to vegetation structure, flock characteristics and constituents (especially for understory specialists). Importantly, forest succession affected flock patterns particularly in relation to the flocking propensity of regular species, and the frequency of nuclear species (Huet’s fulvetta Alcippe hueti), which in turn determined flocking occurrence at different successional stands. Canonical correspondence analysis indicated that understory flocking species (mainly Timaliidae babblers) were significantly associated with intact native canopy cover, complex DBH diversity, as well as high densities of dead trees and large trees, representing a maturity level of successional stands. Our study reveals that the effect of natural forest succession on mixed-species bird flocks is species-specific and guild-dependent. From a conservation perspective, despite a high proliferation of pine plantation in southern China, priority should be placed on protecting the advanced forest with a rich collection of understory flocking specialists.     

The effects of microcrustaceans on succession and diversity of an algal microcosm community

Summary The effects of herbivorous microcrustaceans on algal succession and diversity were studied in replicated 200 ml freshwater microcosms. Three different experiments were conducted. Two experiments used laboratory microcosms in growth chambers. Rotenone was used to kill the microcrustaceans in one-half of the cultures. Diversity (H') and succession were monitored over a 60 day period. The third experiment used similar microcosms, but they were kept out of doors. In this experiment, microcrustaceans became extinct in some cultures because of a mechanical disturbance. In all three experiments, succession from a community dominated by green algae to one dominated by blue-green algae was significantly slower when microcrustaceans were present. Diversity was higher in grazed cultures at some times during succession, but not at all times. The dynamics of diversity during succession appear to be governed principally by the change in the relative frequency or green and blue-green algae, rather than by the dynamics of individual species. Nutrient recycling by the microcrustaceans may favor green algae, partially mitigating mortality on green algae due to grazing pressure.     

Local effects of forest fragmentation on diversity of aquatic insects in tropical forest streams: implications for biological conservation

The influence of forest fragmentation (habitat isolation) on biological and ecological diversity of aquatic insects was investigated in streams of fragmented forests in Hulu Gombak (6 streams) and Gunung Angsi (5 streams) and un-fragmented forest of Berembun (6 streams) in peninsular Malaysia. Several environmental parameters including canopy cover, DO, temperature and pH differed significantly among the three catchments (P < 0.05). We found that taxonomic richness in Berembun forest was significantly different from Gunung Angsi (P < 0.05), but not with Hulu Gombak forests (P > 0.05). Nestedness pattern that measures the effect of habitat isolation on taxonomic assemblages showed that aquatic insect’s community in un-fragmented forest (Berembun) was less nested (T = 54.4), indicating high diversity compared to highly nested (less diverse) in the two fragmented forests (Hulu Gombak, T = 30.45 and Gunung Angsi, T = 35.45). Taxa similarity in Berembun streams was negatively correlated with the geographical distance among streams (Mantel test, r = ? 0.462, P < 0.05). Such correlation was absent in both Gunung Angsi and Hulu Gombak streams. Forest fragmentation in Hulu Gombak and Gunung Angsi measured as the distance of the forests from the nearest forested area had negative effect on aquatic insects diversity (r ² = ? 0.149, P < 0.05), but not on their abundances (r ² = 0.003, P > 0.05). We concluded that local habitat conditions were the most important in shaping the aquatic insects community among streams of both unfragmented and fragmented forests.     

The importance of littoral forest remnants for indigenous bird conservation in southeastern Madagascar

The littoral forests of Madagascar are relatively unexplored ecosystems that are considered seriously threatened by deforestation and habitat fragmentation. We set out to describe the bird communities inhabiting the littoral forest remnants in three different sub-regions of southeastern Madagascar to determine the national importance of these forests for bird conservation. In total, 77 bird species were found inhabiting 14 littoral forest remnants. Of these species, 40 are endemic to Madagascar and a further 21 are endemic to the Indian Ocean sub-region, consisting of Madagascar, the Comoros and the Mascarenes. The matrix habitats (Melaleuca forests, marécage swamp forest, Eucalyptus plantations and Erica grassland) that immediately surround the littoral forests were depauperate of bird species and contained few species that were found within the littoral forests. The geographic location of littoral forest remnants had an important role in determining what bird species occurred within them, with the northern remnants having similar bird communities to nearby humid forest whilst the most southern remnant had a bird community that resembled those of nearby spiny forest habitats. Eleven bird species that have been previously described as being habitat-restricted endemics to either spiny forests or humid forests, were found in littoral forest remnants. These results suggest that these littoral forests may play an important transitional role between the two other major natural habitats (spiny forest and humid forest) of southeastern Madagascar. On this basis we advocate that the littoral forest remnants of southeastern Madagascar should be afforded continuing conservation priority.     

Leaf miner assemblies: effects of plant succession and grazing management

Abstract. 1. Changes in leaf-miner assemblies during 4 years of secondary succession, under different controlled sheep-grazing treatments, are described and compared to the miner fauna of older grazed grassland nearby.
2. Multivariate analyses were used in conjunction with examination of individual common species to assess the independent effects of time, grazing treatment, plant species composition and architecture on the leaf-miner assemblies.
3. Leaf-miner species composition was strongly related to plant species composition, but was modified by plant structure under different grazing treatments. There was a strong successional trend in miner assemblies, even when the effects of changes in plant composition had been taken into account. Conversely, local variation in miner species composition generally reflected foodplant distribution alone.
4. Grazed treatments had fewer mines than controls, but there were also species specializing in grazed areas, despite the abundance of their foodplants elsewhere. There was a weak indication that miner species in grazed treatments were more likely to fluctuate in abundance than those in controls.
5. The results are discussed in relation to the assembly of grassland insect communities during succession, and the use of 'indicator groups' in management for nature conservation.     

The landscape ecological approach in bird conservation: integrating the metapopulation concept into spatial planning

In The Netherlands, fragmentation of (semi)natural ecosystems is regarded as a major nature conservation problem. The current Dutch Nature Conservation Policy Plan proposes a spatial network consisting of existing nature reserves, nature redevelopment areas and corridor zones. One of the objectives is to stop the assumed decline of biodiversity due to fragmentation. In this contribution we show that breeding birds are affected by the spatial distribution of their habitat. We also show how problems due to fragmentation can be solved by integrating landscape ecological research data Into planning procedures. Fragmented bird populations show metapopulation characteristics, dependent on the degree of fragmentation. This can be concluded from pattern studies, in which presence or absence patterns are correlated with spatial characteristics. Metapopulation dynamics were used, and the frequency of local extinction and of recolonization were related to size of habitat patches and spatial position in the landscape. The conclusion is that, depending on the spatial scale, landscape fragmentation is a threat to birds. On the basis of empirical data, statistical and metapopulation models are being developed to be used to evaluate spatial planning scenarios and to support decision making about which scenario is closest to the planning aims.     

Coincident scales of forest feedback on climate and conservation in a diversity hot spot

The dynamic relationship between vegetation and climate is now widely acknowledged. Climate influences the distribution of vegetation; and through a number of feedback mechanisms vegetation affects climate. This implies that land-use changes such as deforestation will have climatic consequences. However, the spatial scales at which such feedbacks occur remain largely unknown. Here, we use a large database of precipitation and tree cover records for an area of the biodiversity-rich Atlantic forest region in south eastern Brazil to investigate the forest-rainfall feedback at a range of spatial scales from ca 10(1)-10(4) km2. We show that the strength of the feedback increases up to scales of at least 10(3) km2, with the climate at a particular locality influenced by the pattern of landcover extending over a large area. Thus, smaller forest fragments, even if well protected, may suffer degradation due to the climate responding to land-use change in the surrounding area. Atlantic forest vertebrate taxa also require large areas of forest to support viable populations. Areas of forest of ca 10(3) km2 would be large enough to support such populations at the same time as minimizing the risk of climatic feedbacks resulting from deforestation.     

Finding and promoting a local conservation consensus in a globally important tropical forest landscape

Can democratic processes favour conservation outcomes in the tropics? This study focuses on local viewpoints within a forested landscape of high conservation significance in East Kalimantan (Indonesian Borneo). Stakeholders received posters displaying results from a previous study; these posters emphasised local priorities and views regarding local biodiversity. We assess local attitudes to this information, and consider some implications. Knowledge of, and agreement with, poster content increased among villagers, townspeople and civil servants after they received posters. All respondents appreciated the posters and all supported some form of forest conservation. All respondents agreed that biodiversity conservation and local views are vital in land-use planning. All agreed that logging companies need to be better controlled, while 80% consider them a “major environmental threat”. These results bolster our belief that involving communities is not only an ethically defensible way to achieve conservation outcomes, but also a pragmatic opportunity to do so.     

Optimizing conservation of forest diversity: a country-wide approach in Mexico

A recent vegetation study [Palacio-Prieto et al. (2000) Bol Inst Geogr UNAM 43:183–203] showed that Mexico’s forest area has declined to 33.3%, from originally 52.0% of the country’s land area. In order to assess strategies for tree diversity conservation, we compiled a list of 846 tree species native to Mexico, and determined for each the presence or absence in 234 geographical squares of 1° latitude by 1° longitude (approximately 106 × 106 km). On the average, any two squares shared only 6% of their species composition. Using a standard optimization method from engineering and economics [Dantzig (1963) Linear programming and extensions. Princeton University Press, Princeton, NJ, USA, 625 p], we determined the minimally necessary land area in Mexico to conserve the 846 tree species, while securing that each species is found in an area of (approximately) 1,100 km² of currently existing forest vegetation. Furthermore, we took into account 15 existing protected areas with a size of at least 1,100 km² each. With these constraints, the total minimum area needed to conserve all 846 tree species is 45,136 km² of currently existing forest vegetation, or 2.3% of Mexico’s surface. While this analysis can be refined with subsequent field work, the proposed reserve network indicates that efficient land use planning on a national scale may be able to conserve tree species diversity in a relatively small portion of Mexico, even after severe deforestation has taken place.