Suchergebnisse

This study investigated the effects of habitat clearance and fragmentation on
birds of coastal heathlands in subtropical eastern Australia. Abundance and
species composition were compared among two types of cleared habitat
(residential suburbs and sugar cane cropland) and four sizes of heathland
remnant (1–2 ha, 5–10 ha, 20–50 ha and >500 ha) in summer
and winter. Cleared land contained a distinctly different bird species
assemblage from heathland remnants. Residential sites contained a distinct
suite of species consistent with that described for 'open/developed
land' habitat elsewhere in the region. In contrast, cane cropland
supported very few species. Heathland remnants >500 ha contained high
densities of 'natural-vegetation-dependent' species, whereas
species of open/developed land were absent. Remnants of 1–2 ha had
lowered densities of many natural-vegetation-dependent species, and a
relatively high abundance of open/developed land species. Some of the
avifaunal differences in the >500-ha remnants and 5–50-ha range are
probably due to confounding of remnant size with habitat, resulting from
selective clearing of the landscape. Most of the heathland birds were
intolerant of the matrix habitat (residential and cane cropland), but tolerant
of decreased remnant area, down to a threshold of about 5 ha. However, the
distinctive floristic associations of heathland vegetation are dependent on an
environmental regime (low nutrient, low pH, fire, in some cases inundation)
that is unlikely to persist in remnants tens of hectares in size, and
longer-term declines in heathland birds, are predicted.

The effects on terrestrial fauna of clearing, fragmentation and regeneration
of eucalypt forest and woodland were investigated in a former cattle-grazing
area of south-east Queensland. The abundance of species and higher taxa was
compared among four major habitat types: interior of relatively mature forest,
interior of earlier stages of regenerating forest, cleared pasture, and abrupt
edges between the forest and cleared land. The regenerating sites were several
decades old and consisted mainly of Eucalyptus saplings
3–6 m high, with a grassy understorey.
Numbers of pitfall-trapped invertebrate orders were significantly higher in
forest interior and forest edge than in cleared or regenerating sites; numbers
of coleopterans were significantly higher in forest interior sites than in
cleared or regenerating sites; and numbers of isopterans were significantly
higher in both forest interior and forest edge sites than in cleared sites.
Total abundance of native non-flying mammals was significantly higher in
forest interior than elsewhere. Other vertebrates apart from birds were
detected in numbers too low for analysis. Cleared sites supported
significantly lower numbers of avian species and Orders, and of total birds,
than any other habitat in winter, with a similar but non-significant trend in
summer. Forest interior sites showed a significantly higher abundance of
several avian species than any other habitat, but noisy miners and Torresian
crows were significantly more abundant in edge sites than in forest interior
sites. Sites of low regeneration were chiefly utilised by birds characteristic
of forest edge. Many decades of regeneration would appear to be necessary
before many forest-dependant species are adequately supported in these areas.

Variation in bird assemblages associated with forest clearing and urbanisation
in the greater Brisbane area was assessed by counting birds in sites within
six habitat categories: large remnants, small remnants, no- understorey
remnants, canopy suburbs (original trees present), planted suburbs, and bare
suburbs. Total bird abundance and species richness were generally highest in
canopy suburbs. Individual species showed many significant abundance
differences among the habitat types, and were classified into three major
response categories: bushland species (3 in summer, 13 in winter), tolerant
species (13 in summer, 13 in winter), and suburban species (12 in summer, 11
in winter).
The commonly proposed notion that urbanisation results in lowered bird species
richness and increases in introduced species is broadly consistent with the
observed differences between bare suburbs and large remnants. However, it does
not adequately describe the situation in the planted and canopy suburbs, where
there was high species richness and extremely high abundance of some native
species (including noisy miners, lorikeets, friarbirds, and butcherbirds) but
low abundance of a majority of the species common in the original habitats
(including fantails, wrens, whistlers, and other small insectivores). Retained
forest remnants are essential for the latter group. Urban plantings of
prolifically flowering native species do not reverse the effects of
deforestation, but promote a distinctive group of common native suburban bird
species. Origins of the urban bird assemblage are discussed.

Obtaining adequate information for informed conservation-management decisions requires effective and cost-efficient survey techniques. We compared the effectiveness of bat detectors and harp traps for surveying bat assemblages within an urban landscape in Brisbane, Australia, with respect to number and composition of species. Nine sites within each of three habitat types (remnant bushland, parkland, and low-density residential – a total of 27 sites) were sampled twice each. The bat detectors recorded 3628 calls, from which 13 taxa were identified. The harp traps captured 17 individuals, from which five taxa were identified. All species captured by harp trap were also detected by bat detector, with the possible exception of N. bifax. Bat detectors recorded significantly more species per site than were captured by harp traps, both overall and within each of the three habitat types. And although a considerable amount of time and expense was required to identify the recorded echolocation calls to species, bat detectors were also the most cost-efficient sampling method. These results collectively show that bat detectors were the most effective and cost-efficient method for surveying the bat assemblage in this urban landscape.

[Extract] Land clearing has returned to Queensland in a big way. After we expressed concern that policy changes since 2012 would lead to a resurgence in clearing of native vegetation, this outcome was confirmed by government figures released late last year. It is now clear that land clearing is accelerating in Queensland. The new data confirm that 296,000 hectares of bushland was cleared in 2013-14 – three times as much as in 2008-09 – mainly for conversion to pastures. These losses do not include the well-publicised clearing permitted by the government of nearly 900 square kilometres at two properties, Olive Vale and Strathmore, which commenced in 2015.

Tropical reforestation (TR) has been highlighted as an important intervention for climate change mitigation because of its carbon storage potential. TR can also play other frequently overlooked, but significant, roles in helping society and ecosystems adapt to climate variability and change. For example, reforestation can ameliorate climate-associated impacts of altered hydrological cycles in watersheds, protect coastal areas from increased storms, and provide habitat to reduce the probability of species' extinctions under a changing climate. Consequently, reforestation should be managed with both adaptation and mitigation objectives in mind, so as to maximize synergies among these diverse roles, and to avoid trade-offs in which the achievement of one goal is detrimental to another. Management of increased forest cover must also incorporate measures for reducing the direct and indirect impacts of changing climate on reforestation itself. Here we advocate a focus on "climate-smart reforestation," defined as reforesting for climate change mitigation and adaptation, while ensuring that the direct and indirect impacts of climate change on reforestation are anticipated and minimized.