Tag Archives for drop

Australian fished populations drop by a third over ten years, study finds


Graham Edgar, University of Tasmania and Trevor J Ward, University of Technology Sydney

Large fish species are rapidly declining around Australia, according to the first continental diver census of shallow reef fish. Contrary to years of sustainability reports, our study indicates that excessive fishing pressure is contributing to decline of many Australian fish species.

In areas open to fishing, we found that exploited populations fell by an average of 33% between 2005 and 2015. This rate closely matches the 32% downward trend in total Australian fishery catches through the same period.



Read more:
Citizen scientist scuba divers shed light on the impact of warming oceans on marine life

In contrast, in marine parks where fishing is prohibited, the same species increased by an average of 25%. Other species not targeted by fishers showed a small downward trend (11% decline in fished zones; 16% decline in no-take marine reserves), indicating that recent marine heatwaves off southeastern and southwestern Australia have probably adversely affected marine life over a wide area.



Read more:
Marine heatwaves are getting hotter, lasting longer and doing more damage

Citizen science

Our audit of 531 study sites was made possible by combining data from 50-metre long transects repeatedly surveyed by Australian Institute of Marine Science and University of Tasmania research divers, and by highly trained volunteers participating in the citizen science Reef Life Survey program.

After the collapse of some high-profile fisheries in the 1990s, such as gemfish, orange roughy and southern bluefin tuna, federal and state agencies took a more conservative approach to fish capture. Australian fisheries are now regarded as among the most sustainable worldwide.



Read more:
Plenty of fish in the sea? Not necessarily, as history shows

Regardless, the prevalence of downward population trends in our investigation indicates that a reduction in fishing pressure and additional caution is needed. Otherwise, more Australian fisheries may not be economically viable if this trend continues.

Our analysis identified a variety of issues that affect fishery management practices, many of which are also evident overseas, including:

  • little relevant data for decision-making related to ecological issues
  • a lack of no-fishing reference areas to scientifically assess impacts of fishing
  • poorly documented stock assessments with limited public accessibility
  • management decisions made by committees dominated by industry-aligned members
  • short-term catch maximisation prioritised over precaution
  • fishery models that rarely consider species interactions or climate impacts
  • wider effects of fishing on ecosystems and their resilience to multiple pressures are overlooked

No-fishing reserves work

Our study indicates that a highly effective but underused tool in the manager’s toolbox is expanded rollout of no-fishing “marine reserves”. Despite receiving wide public support, most Australian marine reserves are small and located in areas with few fishery resources. They consequently house few mature, egg-producing females and do little to assist in the rebuilding of overfished stocks. Nor are they likely to help much in the recovery of important ecosystem functions, as needed for fished-species populations to rebound after climate shocks and other pressures.

The July rollout of Australian Marine Parks, in particular, represents a lost opportunity that may prove a significant problem for fishers. Although covering 2.76 million square kilometres – the largest marine park in the world – it is of limited conservation value.



Read more:
Australia’s new marine protected areas: why they won’t work

Through three rounds of public submissions, each largely aimed at minimising any remaining overlap with current fishing activities, the final zoning plans affect very few stakeholders. The outcome is neither an efficient nor effective solution to the actual problem of protecting the oceans.

For example, the Temperate East Zone covering waters from the Victorian border to southern Queensland includes no new “no-take” reserves shallower than 1,000m depth, although these waters are where virtually all fishing impacts occur in this region.

The widespread declaration of marine parks that allow current fishing to continue is perhaps useful when harmful fishing practices for ecosystems are excluded. However, our study indicates that this basic assumption does not apply to Australian Marine Parks.



Read more:
More than 1,200 scientists urge rethink on Australia’s marine park plans

The ConversationThe environmental and economic debt for future generations is both huge and unfair.

Graham Edgar, Senior Marine Ecologist, Institute for Marine and Antarctic Studies, University of Tasmania and Trevor J Ward, Adjunct professor, University of Technology Sydney

This article was originally published on The Conversation. Read the original article.

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River flows drop as carbon dioxide creates thirstier plants


Anna Ukkola, UNSW Australia and Albert Van Dijk, Australian National University

Rising carbon dioxide concentrations are causing vegetation across large parts of Australia to grow more quickly, in turn consuming more water and reducing flows into river basins.

Our research, published today in Nature Climate Change, shows that river flows have decreased by 24-28% in a large part of Australia due to increasing CO₂ levels, which have risen by 14% since the early 1980s.

This could exacerbate water scarcity in several populated and agriculturally important regions.

Contrasting effects

It was previously unclear whether the increasing CO₂ in the atmosphere has led to detectable changes in streamflow in Australian rivers. This is partly because increasing CO₂ can have two opposing effects on water resources.

CO₂ is the key ingredient for photosynthesis, and higher concentrations allow plants to grow more vigorously. This fertilisation effect could be expected to lead to denser vegetation that needs more water to grow, in turn reducing the amount of rainwater that can run off into rivers.

Acting directly against this is the fact that increased CO₂ concentrations allow plants to use water more sparingly. Small pores called stomata on the surface of leaves allow plants to regulate their uptake of CO₂ for photosynthesis and water loss to the atmosphere. At higher CO₂ concentrations, plants can partially close these pores, maintaining the same influx of CO₂ while also reducing water loss through transpiration. This could be expected to leave more rainwater available to become river runoff.

The net effect of these two counteracting processes has so far been highly uncertain. In our study, we used a new method that combines satellite measurements of vegetation cover with river flow data collected for over 30 years. Using statistical methods we factored out other influences that affect river flows, such as variations in rainfall.

Our results suggest that the net effect of increased CO₂ has been declining runoff across the subhumid and semi-arid parts of Australia, and that this can be attributed to the increased vegetation.

Reduced streamflow due to CO2-induced vegetation greening was observed in subhumid and semi-arid climates.
Anna Ukkola, Author provided

The good news is that increasing CO₂ might also make plants better able to survive in these drying landscapes. By using water more efficiently, plants can grow more vigorously in arid regions and should better withstand droughts, such as those commonly associated with El Niño events. In areas with an average annual rainfall below about 700 mm, we found that the amount of vegetation cover that can be sustained has increased by about 35% since the early 1980s. This is good news for dryland cropping and grazing which are likely to enjoy increased yields as a consequence.

Despite these positive effects, in less dry parts of Australia, the reduction of river flow adds yet more pressure to water resources. As natural vegetation is greening and consuming more water, local rivers and dams are receiving less. At the same time, rainfall patterns are changing. With the exception of northern Australia, many of the affected areas are already experiencing declining rainfall and this trend is projected to continue into the future with increasing global temperature.

Elsewhere around the world, vegetation increases have also been observed in other dry regions such as southern and western Africa and the Mediterranean. It is certainly possible that these regions are also facing declining streamflow as a result.

The increase in vegetation helps to draw CO₂ from the atmosphere, but the effect is not enough to significantly slow the rise in atmospheric CO₂ and the resulting long-term climate change. Despite the observed greening, most of Australia’s vegetation continues to be very sensitive to rainfall changes. If rainfall continues to decline as projected, the greening trend may end or even be reversed, releasing the stored carbon back into the atmosphere.

The Conversation

Anna Ukkola, Research Associate, Climate Change Research Centre, UNSW Australia and Albert Van Dijk, Professor of Water Science and Management, Fenner School of Environment & Society, Australian National University

This article was originally published on The Conversation. Read the original article.

Destination: Back Packing Holiday


I have pretty much determined that my holiday is going to be a back packing trip through the wilderness along the ‘Tops to Myall’s Heritage Trail.’ Now I need to decide on just what part of the trail I’ll do, if indeed not all of it.

One of the determining factors for the trip will be the availability of transport. I would need to get to the Barrington Guesthouse in order to start the walk if doing the whole walk, or either get home from the Gloucester area or to the Gloucester area to start the walk. The start from near Gloucester wouldn’t be an issue – that would be fairly easy to solve with Countrylink and family I think (combo). I’m not sure about the Guesthouse option just yet, but looking into it a little. I could easily walk from where I live to the Gloucester area (and for that matter do a return walk if necessary – though I’d prefer to not do so). I also think that Countrylink could easily drop me off near the start of the walk up that way (along the Buckets Way) should that be necessary.

The most likely outcome is that I’ll travel to Gloucester with Countrylink and then get a lift to the walk starting point from my family the next day. I could try getting a lift to the guesthouse with the family also, but that is unlikely to be an option I would think.