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Published: 12 September 2011

Breaking up not always bad for reefs


Fragmentation of coral reefs may in some cases assist in recolonisation of reef species, according to a recent study of coral reef recovery in Papua New Guinea.

Reef fragmentation may reduce competition between species recolonising damaged coral reefs.
Credit: Mary Bonin

In the study, three researchers from the ARC Centre of Excellence for Coral Reef Studies and James Cook University constructed 30 artificial coral reefs from hundreds of tonnes of rock and gravel at Kimbe Bay, PNG.

‘When a reef suffers a heavy impact – such as a storm or outbreak of coral bleaching – there are two different effects on the coral habitat,’ explained one of the researchers, Dr Mary Bonin.

‘First, a lot of the habitat that was once available to fish is totally lost. Second, the habitat that still remains is often fragmented, or broken up into smaller patches.

‘We wanted to figure out if the increased habitat patchiness is actually a problem for coral reef fishes, or whether it is really the loss of habitat that causes fish to decline following an impact.’

Working with colleagues Professor Geoff Jones and Dr Glenn Almany, Dr Bonin topped each artificial reef with a square metre of living bottlebrush coral and stocked it with 20 small blue and yellow damselfish. They observed that the reef would eventually acquire richer diversity as baby fish came in on the current and settled.

The scientists then simulated habitat loss, fragmenation and a combination of the two processes.

‘As you’d expect, the effects of a loss of 75 per cent of the habitat were awful. With most of their home gone, the fish just disappeared,’ said Dr Bonin.

‘But when we divided some of the reefs into three separate parts, we found that fish survival and diversity actually improved for a time.

‘We think this is because a fragmented or patchy habitat reduces the competition between fishes, creating more room for the weaker ones or for newcomers to settle.’

This finding challenges a widely-held view that habitat fragmentation always leads to a dramatic loss of fish numbers and diversity.

‘Our findings suggest that it is actually habitat loss that is the major problem for coral reef fishes following an impact,’ Dr Bonin said.

‘The fact that habitat patchiness can have a positive effect on fish diversity is really exciting because it means that even if it isn’t possible for managers to restore an entire coral reef, it will still be highly beneficial to restore small patches of habitat.’

Source: ARC Centre of Excellence for Coral Reef Studies







Published: 26 September 2011

Renewable energy sector to benefit from wind-speed research

Craig Macaulay

While some recent international studies have shown a decrease in wind speeds in several parts of the globe, including Australia, more recent results from CSIRO show that Australia’s average wind speed is actually increasing.

The ability to accurately quantify long-term variations in wind speeds is essential to the viability of Australia’s wind power sector.
The ability to accurately quantify long-term variations in wind speeds is essential to the viability of Australia’s wind power sector.
Credit: Gregory Heath

CSIRO scientists have analysed wind speed observations to understand the causes of variations in near-ground-level wind and explore long-term wind speed trends.

Accurate estimates of long-term trends provide a useful indicator for circulation changes in the atmosphere and are invaluable for the planning and financing of sectors such as wind energy, which need to map risk management under a changing climate.

‘We have a good picture of wind energy availability across Australia from previous CSIRO wind mapping and, with the growth of wind farms, there is an emerging need to understand how climate change can affect the wind resource,’ says Dr Alberto Troccoli, lead author of a recent paper published in Journal of Climate. 1

‘Wind power production is expected to increase greatly over the coming years and the associated electricity system will be subject to variations of several hundred megawatts – depending on wind availability.

‘The ability to quantify with accuracy these long-term variations is essential to the sector from an economic point of view.’

Dr Troccoli said that, averaged across Australia over 1989–2006, wind speeds measured at a height of 10 metres had increased by 0.69 per cent per annum, compared to a decline of 0.36 per cent per annum for wind speeds measured at 2m height.

‘The potential for increasing the efficiency of energy operations by using quality weather and climate information is therefore apparent and one of the first steps is the standardisation of wind recording stations.

‘Wind observations, like other meteorological variables, are sensitive to the conditions in which they are observed – for example, where the instrumentation sits relative to topographical features, vegetation and urban developments.’

The team found that the wind speed trends over Australia are sensitive to the height of the station, with winds measured at 10m displaying an opposite and positive trend to those reported by a previous study, which analysed only winds measured at 2m.

Light winds measured at 10m, a height that represents better the free atmospheric flow, tend to increase more rapidly than the average, whereas strong winds increase less rapidly than the average winds. Light and strong wind measured at a height of 2m tend to vary in line with the average winds.

‘Our work shows a number of challenges with the consistency of the observations during their period of operation and between sites across Australia,’ adds Dr Troccoli.

‘The quality of future wind observational datasets will depend on having consistency between sites, particularly with respect to measurement procedure, maintenance of instrumentation, and detailed records of the site history.’

He said the work has implications for a variety of sectors beyond wind energy including building construction, coastal erosion, and evaporation rates.

The conjunction of energy and meteorology is the central theme of the International Conference Energy & Meteorology on the Gold Coast in November.

Read Dr Troccoli’s thoughts on What’s the energy forecast? Bringing meteorology and generation together in the online forum, The Conversation.


1 A. Troccoli, K. Muller, P. Coppin, R. Davy, C. Russell and A. Hirsch (2011) Long-term wind speed trends over Australia. Journal of Climate, doi: 10.1175/2011JCLI4198.1




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