Michael Bodley Dale

Relationships between anopheline mosquitoes and topography in West Timor and Java, Indonesia

BackgroundMalaria is a serious health issue in Indonesia. Mosquito control is one aspect of an integrated malaria management programme. To focus resources on priority areas, information is needed about the vectors and their habitats. This research aimed to identify the relationship between anopheline mosquitoes and topography in West Timor and Java.MethodsStudy areas were selected in three topographic types in West Timor and Java. These were: coastal plain, hilly (rice field) and highland. Adult mosquitoes were captured landing on humans identified to species level and counted.ResultsEleven species were recorded, four of which were significant for malaria transmission: Anopheles aconitus, Anopheles barbirostris, Anopheles subpictus and Anopheles sundaicus. Each species occupied different topographies, but only five were significantly associated: Anopheles annularis, Anopheles vagus and Anopheles subpictus (Java only) with hilly rice fields; Anopheles barbirostris, Anopheles maculatus and Anopheles subpictus (West Timor only) with coastal areas.ConclusionInformation on significant malaria vectors associated with specific topography is useful for planning the mosquito control aspect of malaria management.

A conceptual model for integrating physical geography research and coastal wetland management, with an Australian example

We have developed a conceptual model to assist integration between physical geographical sciences, institutional frameworks and management in the context of coastal wetlands. Wetlands are key interconnected systems that will respond early to climate change and especially to associated sea-level changes. A major constraint on management of wetlands is the lack of congruence between the ecosystems and the institutional frameworks that govern their management: connectivity in coastal systems is overlain by institutional fragmentation. We introduce a model that facilitates integration of physical geographical (biophysical) information into the legislative, planning, policy and management process. It consists of interconnected parallel subprojects in science and in planning with strong cross-links with stakeholders at all levels, founded on long-term and trusting relationships. We also show progress that has been made in applying the model, with an Australian example. It is concluded that the approach has potential to move towards the goal of sustainable management but that it urgently needs to evolve, so as to meet the challenges of climate and associated changes.

Assessing impacts of small perturbations using a model-based approach.

When examining the effects of a disturbance on a complex system like vegetation it is difficult to distinguish between those changes that affect the processes underlying the functioning of the system and other changes which simply shift the state of the system but have no effect on the processes. The former is obviously a more significant effect than the latter. In this paper we examine a model-based clustering procedure which can make such a distinction. Given observations on several sites on several occasions, we model the dynamics of the processes using a continuous hidden Markov model. In this model the actual Markov process is hidden, but at any observation time we can observe surrogate variables whose values will be conditional on the underlying state of the process. We further ask if there is evidence for more than one such process, i.e. whether our data are heterogeneous. By estimating the number of clusters using a Bayesian information criterion we can choose between these alternatives. An analogous assessment is made of the number of states in the underlying hidden Markov models, as well as the transition matrices between states and emission probabilities relating the underlying hidden state to the observed attributes. The methodology was applied to the question of determining if a runnelling treatment of a salt marsh for mosquito management had changed the underlying processes related to the vegetation.

Using Markov models to incorporate serial dependence in studies of vegetation change.

In this paper, we re-examine data from an intertidal salt-marsh, recording changes over 14 years. We use a method that explicitly accounts for possible temporal dependency between successive observations. This method employs first-order Markov models. We compare this with other methods used to explore these data without regard for serial dependence, and also investigate whether a higher-order Markov process is desirable. Although a salt-marsh has strong gradients, which might suggest continuous change, the results suggest that, in terms of major processes, two distinct communities are present with relatively weak linkages between them.

Measuring information-based complexity across scales using cluster analysis.

Scaling of ecological data can present a challenge firstly because of the large amount of information contained in an ecological data set, and secondly because of the problem of fitting data to models that we want to use to capture structure. We present a measure of similarity between data collected at several scales using the same set of attributes. The measure is based on the concept of Kolmogorov complexity and implemented through minimal message length estimates of information content and cluster analysis (the models). The similarity represents common patterns across scales, within the model class. We thus provide a novel solution to the problem of simultaneously considering data structure, model fit and scale. The methods are illustrated in application to an ecological data set.

Aspects of Adaptive Management of Coastal Wetlands: Case Studies of Processes, Conservation, Restoration, Impacts and Assessment

Coastal wetlands are dynamic and include the freshwater-intertidal interface. In many parts of the world such wetlands are under pressure from increasing human populations and from predicted sea-level rise. Their complexity and the limited knowledge of processes operating in these systems combine to make them a management challenge. Adaptive management is advocated for complex ecosystem management (Hackney 2000; Meretsky et al. 2000; Thom 2000; National Research Council 2003). Adaptive management identifies man- agement aims, makes an inventory/environmental assessment, plans manage- ment actions,implements these, assesses outcomes, and provides feedback to iterate the process (Holling 1978; Walters and Holling 1990). This allows for a dynamic management system that is responsive to change.

Mosquito Longevity, Vector Capacity, and Malaria Incidence in West Timor and Central Java, Indonesia

The aim of this paper was to relate anopheline mosquito longevity to malaria incidence in two areas in Indonesia: West Timor and Central Java. We estimated the physiological age of females captured landing on humans or resting inside and outside buildings. The estimate was based on the state of the ovaries and was used to estimate longevity. The results showed that there were large differences between the two areas surveyed. In West Timor the longevity of the anophelines ranged from 13 to 23 days, sufficient for completing the intrinsic incubation cycle and for malaria transmission, whereas in Central Java the longevity was only 3 days, insufficient both for incubation and for transmission. We concluded that the West Timor study area had a greater risk of malaria transmission than that of Central Java and this was supported by village survey data that showed greater malaria incidence in West Timor than in Central Java.