25 research outputs found
An artificial diet for continuous rearing of the coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera : Scolytidae)
Using the past to constrain the future: how the palaeorecord can improve estimates of global warming
Climate sensitivity is defined as the change in global mean equilibrium
temperature after a doubling of atmospheric CO2 concentration and provides a
simple measure of global warming. An early estimate of climate sensitivity,
1.5-4.5{\deg}C, has changed little subsequently, including the latest
assessment by the Intergovernmental Panel on Climate Change.
The persistence of such large uncertainties in this simple measure casts
doubt on our understanding of the mechanisms of climate change and our ability
to predict the response of the climate system to future perturbations. This has
motivated continued attempts to constrain the range with climate data, alone or
in conjunction with models. The majority of studies use data from the
instrumental period (post-1850) but recent work has made use of information
about the large climate changes experienced in the geological past.
In this review, we first outline approaches that estimate climate sensitivity
using instrumental climate observations and then summarise attempts to use the
record of climate change on geological timescales. We examine the limitations
of these studies and suggest ways in which the power of the palaeoclimate
record could be better used to reduce uncertainties in our predictions of
climate sensitivity.Comment: The final, definitive version of this paper has been published in
Progress in Physical Geography, 31(5), 2007 by SAGE Publications Ltd, All
rights reserved. \c{opyright} 2007 Edwards, Crucifix and Harriso
Absolute Proper Motions to B~22.5: IV. Faint, Low Velocity White Dwarfs and the White Dwarf Population Density Law
The reduced proper motion diagram (RPMD) for a complete sample of faint stars
with high accuracy proper motions in the North Galactic Pole field SA57 is
investigated. Eight stars with very large reduced proper motions are identified
as faint white dwarf candidates. We discriminate these white dwarf candidates
from the several times more numerous QSOs based on proper motion and
variability.
We discuss the implausibility that these stars could be any kind of survey
contaminant. If {\it bona fide} white dwarfs, the eight candidates found here
represent a portion of the white dwarf population hitherto uninvestigated by
previous surveys by virtue of the faint magnitudes and low proper motions. The
newly discovered stars suggest a disk white dwarf scaleheight larger than the
values of 250-350 pc typically assumed in assessments of the local white dwarf
density. Both a <V/V_{max}> and a more complex maximum likelihood analysis of
the spatial distribution of our likely thin disk white dwarfs yield
scaleheights of 400-600 pc while at the same time give a reasonable match to
the local white dwarf volume density found in other surveys.
Our results could have interesting implications for white dwarfs as potential
MACHO objects. We can place some direct constraints (albeit weak ones) on the
contribution of halo white dwarfs to the dark matter of the Galaxy. Moreover,
the elevated scale height that we measure for the thin disk could alter the
interpretation of microlensing results to the extent of making white dwarfs
untenable as the dominant MACHO contributor. (Abridged)Comment: 38 pages, 5 figures, to appear in April Ap
Reflecting on research produced after more than 60 years of exclosures in the Kruger National Park
All data, in this case works of literature reviewed have been
summarised in Online Appendix 2.Herbivores are a main driver of ecosystem patterns and processes in semi-arid savannas, with their effects clearly observed when they are excluded from landscapes. Starting in the 1960s, various herbivore exclosures have been erected in the Kruger National Park (KNP), for research and management purposes. These exclosures vary from very small (1 m2) to relatively large (almost 900 ha), from short-term (single growing season) to long-term (e.g. some of the exclosures were erected more than 60 years ago), and are located on different geologies and across a rainfall gradient. We provide a summary of the history and specifications of various exclosures. This is followed by a systematic overview of mostly peer-reviewed literature resulting from using KNP exclosures as research sites. These 75 articles cover research on soils, vegetation dynamics, herbivore exclusion on other faunal groups and disease. We provide general patterns and mechanisms in a synthesis section, and end with recommendations to increase research outputs and productivity for future exclosure experiments. CONSERVATION IMPLICATIONS : Herbivore exclosures in the KNP have become global research platforms, that have helped in the training of ecologists, veterinarians and field biologists, and have provided valuable insights into savanna dynamics that would otherwise have been hard to gain. In an age of dwindling conservation funding, we make the case for the value added by exclosures and make recommendations for their continued use as learning tools in complex African savannas.South African Environment Observation Network (SAEON).http://www.koedoe.co.zaam2023Paraclinical Science