The Darling River is simply not supposed to dry out, even in drought



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Puddles in the bed of the Darling River are a sign of an ecosystem in crisis.
Jeremy Buckingham/Flickr, CC BY-SA

Fran Sheldon, Griffith University

The deaths of a million of fish in the lower Darling River system over the past few weeks should come as no surprise. Quite apart from specific warnings given to the NSW government by their own specialists in 2013, scientists have been warning of devastation since the 1990s.

Put simply, ecological evidence shows the Barwon-Darling River is not meant to dry out to disconnected pools – even during drought conditions. Water diversions have disrupted the natural balance of wetlands that support massive ecosystems.

Unless we allow flows to resume, we’re in danger of seeing one of the worst environmental catastrophes in Australia.




Read more:
Explainer: what causes algal blooms, and how we can stop them


Dryland river

The Barwon-Darling River is a “dryland river”, which means it is naturally prone to periods of extensive low flow punctuated by periods of flooding.

However, the presence of certain iconic river animals within its channels tell us that a dry river bed is not normal for this system. The murray cod, dead versions of which have recently bought graziers to tears and politicians to retch, are the sentinels of permanent deep waterholes and river channels – you just don’t find them in rivers that dry out regularly.

Less conspicuous is the large river mussel, Alathyria jacksoni, an inhabitant of this system for thousands of years. Its shells are abundant in aboriginal middens along the banks. These invertebrates are unable to tolerate low flows and low oxygen, and while dead fish will float (for a while), shoals of river mussels are probably dead on the river bed.

This extensive drying event will cause regional extinction of a whole raft of riverine species and impact others, such as the rakali. We are witnessing an ecosystem in collapse.

Catastrophic drying

We can see the effects of permanent drying around the world. The most famous example is the drying of the Aral Sea in Central Asia. Once the world’s fourth largest inland lake, it was reduced to less than 10% of its original volume after years of water extraction for irrigation.

The visual results of this exploitation still shock: images of large fishing boats stranded in a sea of sand, abandoned fishing villages, and a vastly changed microclimate for the regions surrounding the now-dry seabed. Its draining has been described as “the world’s worst environmental disaster”.




Read more:
Humans drained the Aral Sea once before – but there are no free refills this time round


So, what does the Aral Sea and its major tributaries and the Darling River system with its tributary rivers have in common? Quite a lot, actually. They both have limited access to the outside world: the Aral Sea basin has no outflow to the sea, and while the Darling River system connects to the River Murray at times of high flow, most of its water is held within a vast network of wetlands and floodplain channels. Both are semi-arid. More worryingly, both have more the 50% of their average inflows extracted for irrigation.

There is one striking difference between them. The Aral Sea was a permanent inland lake and its disappearance was visually obvious. The wetlands and floodplains of the Barwon-Darling are mostly ephemeral, and the extent of their drying is therefore hard to visualise.




Read more:
It’s time to restore public trust in the governing of the Murray Darling Basin


An orphaned ship in former Aral Sea, near Aral, Kazakhstan.
Wikipedia

All the main tributaries of the Darling River have floodplain wetland complexes in their lower reaches (such as the Gwydir Wetlands, Macquarie Marshes and Narran Lakes). When the rivers flow they absorb the water from upstream, filling before releasing water downstream to the next wetland complex; the wetlands acting like a series of tipping buckets. Regular river flows are essential for these sponge-like wetlands.

So, how has this hydrological harmony of regular flows and fill-and-spill wetlands changed? And how does this relate to the massive fish kills we are seeing in the lower Darling system?




Read more:
How is oxygen ‘sucked out’ of our waterways?


While high flows will still make it through the Barwon-Darling, filling the floodplains and wetlands, and connecting to the River Murray, the low and medium flow events have disappeared. Instead, these are captured in the upper sections of the basin in artificial water storages and used in irrigation.

This has essentially dried the wetlands and floodplains at the ends of the tributaries. Any water not diverted for irrigation is now absorbed by the continually parched upstream wetlands, leaving the lower reaches vulnerable when drought hits.

By continually keeping the Barwon-Darling in a state of low (or no) flow, with its natural wetlands dry, we have reduced its ability to cope with extended drought.




Read more:
Why a wetland might not be wet


While droughts are a natural part of this system and its river animals have adapted, they can’t adjust to continual high water caused in some areas by water diversions – and they certainly can’t survive long-term drying.

The Basin Plan has come some way in restoring some flows to the Barwon-Darling, but unless we find a way to restore more of the low and medium flows to this system we are likely witnessing Australia’s worst environmental disaster.




Read more:
It will take decades, but the Murray Darling Basin Plan is delivering environmental improvements


The Conversation


Fran Sheldon, Professor, Australian Rivers Institute, Griffith University, Griffith University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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It’s time to restore public trust in the governing of the Murray Darling Basin



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Going all the way back: rules for the Murray Darling Basin are in Australia’s constitution.
KnitSpirit/Flickr, CC BY-NC-SA

Jason Alexandra, RMIT University

Fish deaths in the Darling River have once more raised the public profile of incessant political controversies about the Murray Darling Basin. These divisive debates reveal the deeply contested nature of reforms to water policy in the Basin.

It feels like Australia has been here before – algae blooms are not uncommon in these rivers. In 1992, the Darling suffered the world’s largest toxic algal bloom, over 1,000 kilometres long. This crisis became an iconic catalyst, and helped prompt the state and federal governments agreeing to water reforms in 1994.

Hopefully, our current crisis may be an opportunity to shine a strong light on the complexities of governing the Basin, and initiate the meaningful reforms needed to restore public trust.




Read more:
How is oxygen ‘sucked out’ of our waterways?


Forewarned is forearmed

The rivers of the basin are unique and precious. Australia needs high quality and independent science to understand them and guide their management. Unfortunately in 2012 state and federal governments cut three important programs that provided vital research on the Basin’s rivers:

So while yesterday’s announcement of A$5 million funding to a new native fish recovery program is welcome, good science alone is not enough. Good policy processes and robust institutions are needed to apply this information. We cannot continue to ignore expert warnings.

A crisis of trust

Since a 2017 Four Corners program exposed disturbing allegations of water theft and corruption, the media has revealed a host of further probity issues.

These and a plethora of formal inquiries into MDB governance indicates a crisis of trust, legitimacy and public confidence – in short, a loss of authority.

The 2018 federal Senate inquiry documents a litany of concerns, while disturbing evidence given at a South Australian Royal Commission raised substantive doubts about failures to heed the best scientific advice in the development of the Basin Plan.




Read more:
Explainer: what causes algal blooms, and how we can stop them


More Commonwealth oversight is not enough

Without doubt pressure is mounting for more reforms. The Senate’s Rural and Regional Affairs Committee and the Productivity Commission have recommended splitting the Murray Darling Basin Authority into two entities – the MDB Corporation and a MDB Regulator – in order to clearly separate the Commonwealth’s regulatory oversight from other roles.

These proposals deserve critical scrutiny. Structural reorganisation can provide an illusion of government action, but can have long-term effects on the efficacy and justice of water governance.

The Murray Darling has a unique place in Australia’s history, environment, economy and culture. Agreements about its governance have their origins in debates leading up to Federation in 1901. Any renegotiation needs to respect the Constitution and the different legal powers of the states and the Commonwealth.

So reform to institutional arrangements need bespoke design. These are the legitimate remit of our discursive democracy. Nonetheless, the OECD’s 12 water governance principles usefully provide guidance about the need for clarity of roles, transparency, effectiveness, efficiency and broad stakeholder engagement.

Current calls for reorganisation focus on clarifying the Commonwealth’s regulatory role, but this is fairly narrow. Reforms are needed at all scales.

The governance challenges in the MDB require modernisation and redesign of arrangements across regional, state and Commonwealth agencies. This includes structuring “constructive tensions” that ensure transparency and accountability. Just like the police don’t control the courts, we need to more clearly define and separate roles in the water sector.

Embracing radical transparency

We need all water agencies to adopt a formal charter of transparency and openness. All state and Commonwealth agencies should open their books to scrutiny, rather than hiding information behind claims of “commercial in confidence” or opaque “freedom of information” processes.

Greater transparency measures should also be a condition of all water licences. It’s entirely feasible to create modern monitoring regimes, using state-of-the art digital metering coupled with annual water-use declarations. These would be similar to tax returns enforced with random audits and satellite verification of areas irrigated. If made publicly available, all interested parties could audit water extractions.

But doubts don’t exclusively focus on irrigators’ compliance. We also need to address the states and their willingness and capability to enforce regulations. Policies of radical transparency could be supported with openly available water data. With digital meters and automated gauging of river flows, we could create a computer platform where anybody could develop river models using real data, in near real-time.

Harnessing the power of citizen involvement, trust and openly sharing information has been a hallmark of Australia’s landcare and natural resource management. This is where we should look for the next generation of governance in the Basin.

Open books means communities, industries, research and educational institutions can all help monitor our institutions and ensure rivers are managed in the public’s interest.




Read more:
Recent Australian droughts may be the worst in 800 years


Finally, droughts should not come as surprise. They are a recurrent feature of the Basin. With climate change, more frequent and intense droughts are predicted. As a nation we can do better than lurching from crisis to crisis each time drought returns.

We need careful deliberation about the institutions that will rebuild public confidence and restore trust in the governing of the Murray Darling. It’s time to develop a 21st century system that is cooperative, transparent and just.The Conversation

Jason Alexandra, PhD candidate, RMIT University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How is oxygen ‘sucked out’ of our waterways?



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Dead fish are a source of food for bacteria, which then extract oxygen from the river.
AAP

Stuart Khan, UNSW

A million fish have died in the Murray Darling basin, as oxygen levels plummet due to major algal blooms. Experts have warned we could see more mass deaths this week.




Read more:
Explainer: what causes algal blooms, and how we can stop them


Fingers have been pointed at poor water management after a long period of drought. However, mass fish deaths can also be caused by floods, and even raw sewage.

So what’s going on when oxygen gets “sucked out of the water”?

The phenomenon is very well known to water quality engineers; we call it “biochemical oxygen demand”. To understand it, we need to talk about a little bit of biology and a little bit of chemistry.

When oxygen meets water

Oxygen molecules are soluble in water in the same way that sugar is soluble in water. Once its dissolved, you can’t see it (and, unlike sugar, oxygen is tasteless).

The maximum amount of oxygen that you can dissolve in water depends on a number of factors, including the water temperature, ambient air pressure, and salinity. But roughly speaking, the maximum amount of dissolvable oxygen, known as the “saturation concentration” is typically around 7-10 milligrams of oxygen per litre of water (7-10 mg/L).

This dissolved oxygen is what fish use to breathe. Fish take water in through their mouths and force it through their gill passages. Gills, like our lungs, are full of blood vessels. As water passes over the thin walls of the gills, dissolved oxygen is transferred into the blood and then transported to the fish’s cells. The higher the oxygen concentration in the water, the easier it is for this transfer to occur.

Once in the cells, the oxygen molecules play a key role in the process of “aerobic respiration”. The oxygen reacts with energy-rich organic substances, such as sugars, carbohydrates and fats to break them down and release energy for the cells. The main waste product from this process is carbon dioxide (CO₂). This is why we all need to breathe in oxygen and we breathe out carbon dioxide. Fish do that too. A simple way to express this is:

Organic substances + Oxygen Carbon dioxide + Water + Energy

The Hunter River in NSW suffered a ‘blackwater’ event in 2016 when floodwaters washed organic matter into the river.
Andrew S/Flickr, CC BY-SA

What is the biochemical oxygen demand?

Just like fish and people, many bacteria gain energy from processes of aerobic respiration, according to the simplified chemical reaction shown above. Therefore, if there are organic substances in a waterway, the bacteria that live in that waterway can consume them. This is an important process of “biodegradation” and is the reason our planet is not littered by the carcasses of animals that have died over many thousands of years. But this form of biodegradation also consumes oxygen, which comes from dissolved oxygen in the waterway.

Rivers can replenish their oxygen from contact with the air. However this is a relatively slow process, especially if the water is stagnant (flowing creates turbulence and mixes in more oxygen). So if there is a lot of organic matter present and bacteria are feasting on it, oxygen concentrations in the river can suddenly drop.

Obviously, “organic substances” can include many different things, such as sugars, fats and proteins. Some molecules contain more energy than others, and some are easier for the bacteria to biodegrade. So the amount of aerobic respiration that will occur depends on the exact chemical nature of the organic substances, as well as their concentration.

Therefore, instead of referring to the concentration of “organic substances”, we more commonly refer to the thing that really matters: how much aerobic respiration the organic substances can trigger and how much oxygen this will cause to be consumed. This is what we call the biochemical oxygen demand (BOD) and we usually express it as a concentration in terms of milligrams of oxygen per litre of water (mg/L).

Like us, bacteria don’t consume all of the food which is available to them instantly – they graze on it over time. Biodegradation therefore can take days, or longer. So when we measure the BOD of a contaminated water sample, we need to assess how much oxygen is consumed (per litre of water) over a specified period of time. The standard period of time is usually five days and we refer to this value as the BOD5 (mg/L).

Murray cod pull oxygenated water through their gills, transferring it to their bloodstream. Without oxygen in the water, they die.
Guo Chai Lim/Flickr, CC BY-NC-SA

As I mentioned earlier, clean water might only have a concentration of dissolved oxygen of up to around 7-10 mg/L. So if we add organic material in a concentration which has a higher BOD5 than this, we can expect it to deplete the ambient dissolved oxygen concentration during the next five days.




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More of us are drinking recycled sewage water than most people realise


This phenomena is the main reason for which biological sewage treatment was invented. Raw (untreated) municipal sewage can have a BOD5 of 300-500 mg/L. If this were discharged to a clean waterway, the typical base-level of 7-10 mg/L of oxygen would be consumed, leaving none available for fish or other aquatic organisms.

So the purpose of biological sewage treatment is to grow lots of bacteria in large tanks of sewage and provide them with plentiful oxygen for aerobic respiration. To do this, air can be bubbled through the sewage, or sometimes surface aerators are used to churn up the sewage.

By supplying lots of oxygen, we ensure the BOD5 is effectively consumed while the sewage is still in the tanks, before it’s released to the environment. Well treated sewage can have a BOD5 as low as 5 mg/L, which can then be further diluted as it’s discharged to the environment.

In the case of the Darling river, the high BOD load was created by algae, which died when temperatures dropped. This provided a feast for bacteria, lowering oxygen, which in turn killed hundreds of thousands of fish. Now, unless we clean the river, those rotting fish could become fodder for another round of bacteria, triggering a second de-oxygenation event.The Conversation

Stuart Khan, Professor of Civil & Environmental Engineering, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Explainer: what causes algal blooms, and how we can stop them


Michele Burford, Griffith University

Outbreaks of algae have killed up to a million fish in the Murray Darling Basin over the last two weeks. The phenomena of “algae blooms”, when the population of algae in a river rapidly grows and dies, can be devastating to local wildlife, ecosystems and people. But what are algae blooms? What causes them, and can we prevent them?

Microscopic algae are fundamental to life on earth. These tiny plants provide the fuel that drives marine and freshwater foodwebs, and via photosynthesis, they gobble up carbon dioxide to help counteract emissions, and provide us with oxygen to breathe. Besides rivers, streams, lakes, estuaries and the coast, they can also be found in diverse environments such as snow, soil, and in corals.




Read more:
Are toxic algal blooms the new normal for Australia’s major rivers?


But when humans channel agricultural run-off, sewerage and stormwater discharge into waterways, we dramatically increase the amount of nutrients such as nitrogen and phosphorus. This creates an imbalance, because some microscopic algae are supremely effective at mopping up nutrients and can grow very quickly, dividing up to once a day and quickly overtaking other species. The result is an algal bloom.

Cyanobacteria (blue-green algae) under a microscope.
Author provided

So why don’t we have algal blooms all the time? This is because algae don’t just require nutrients to grow. Like any plant, factors such as temperature and light availability are also important in determining how quickly algae grow and whether they form blooms. Blooms also need slow moving or still water to become established.

In Australia, our algal blooms are typically in freshwaters. The main group of algae responsible for this are known as blue-green algae, or more accurately, cyanobacteria. They regularly bloom in warmer weather in our reservoirs, lakes and slow flowing rivers. In 2016, for example, 1,700km of the Murray River was affected by an algal bloom.

There are many ways they impact the environment and economy. Some algal blooms are toxic, requiring expensive water treatment and – in extreme cases – shutdown of water supplies. This isn’t just a problem in Australia. In 2014, some 500,000 people in the US were left without drinking water due to a toxic algal bloom in Lake Erie.

The toxins can also affect domestic animals, such as dogs, when they drink contaminated water, and limit use of lakes and rivers for swimming, boating and fishing. Even when algal blooms are not toxic, they unbalance the food web, reducing the number of species of animals and plants.

They can also reduce oxygen levels at night, as they switch from photosynthesis (producing oxygen) during the day, to a process called respiration at night where they use oxygen. Low oxygen can stress and even kill fish and other animals if they cannot escape this.

At some point, algal blooms crash when conditions become unsuitable. The resulting dead algae break down, providing an ideal food source for bacteria. This is when waters can become smelly, often with a rotten egg smell. As the bacteria multiply, they suck the oxygen out of the water. At this point, oxygen levels become low both day and night.

If the area of low oxygen is extensive, such as a whole lake or many kilometres of a river system, fish and other animals may not be able to escape to more suitable oxygen levels, and major fish deaths typically occur.

In other areas of the world, algal blooms have caused such severe oxygen conditions that thousands of square kilometres of ocean around the world are now known as dead zones, where no animals can live. These vast dead zones are not something we ever want to see in Australia.

So what can be done about blooms?

There are a wide range of treatments that can be used to control blooms, for example, aerating the water, and adding clays and chemicals, but the catch is they are very expensive on a large scale.

Ideally, the problem should be tackled at the source. This means reducing nutrient loads to our waterways. There has already been progress on this in our cities where sewage treatment plants have been upgraded to reduce nutrient loads to waterways. But tackling nutrients coming from agriculture – erosion, fertilisers, animal waste – is much more challenging and expensive because of the vast areas involved. So this remains work in progress.

It’s also very difficult to predict when blooms will occur; despite being simple plants, algae have an amazing range of strategies to grow and survive. But as we learn more about their complexity our ability to model and predict blooms will improve. This is crucial to managing risks to water supplies and preventing major environmental effects, such as fish deaths.




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Ultimately there are no quick fixes to algal blooms. Given the pressure we put on our waterways, they are here to stay. In fact they are likely to increase due to increasing temperatures and more extreme conditions, such as droughts. We know what we need to do to reduce the scale and likelihood of blooms: the challenge is devoting the resources to achieve it.The Conversation

Michele Burford, Professor – Australian Rivers Institute, and Dean – Research Infrastructure, Griffith University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How we wiped out the invasive African big-headed ant from Lord Howe Island



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Not welcome: the African big headed ant might be small but it can be a pest if it gets in your home.
CSIRO, Author provided

Ben Hoffman, CSIRO

The invasive African big-headed ant (Pheidole megacephala) was found on Lord Howe Island in 2003 following complaints from residents about large numbers of ants in buildings.

But we’ve managed to eradicate the ant completely from the island using a targeted mapping and baiting technique than can be used against other invasive species.

Up to 15% of Lord Howe Island was thought to be infested with the ant.
CSIRO, Author provided

A major pest

The African big-headed ant is one of the world’s worst invasive species because of its ability to displace some native plants and wildlife, and adversely affect agricultural production.




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In an ant’s world, the smaller you are the harder it is to see obstacles


It’s also a serious domestic nuisance. People can become overwhelmed by the large number of ants living in their buildings – you can’t leave a bit of food lying around, especially pet food, or it will be covered in ants.

It remains unclear how long the ant had been on Lord Howe Island, in the Tasman Sea about 770 km northeast of Sydney, before being found. But it is likely to have been present for at least a decade.

Because of the significant threat this ant posed to the conservation integrity of the island, an eradication program was started. But on-ground work done from 2003 to 2011 had many failings and was not working.

In 2011, I was brought in to oversee the program. The last ant colony was killed in 2016, but it is only now, two years later, that we are declaring Lord Howe Island free from the ants.

No African big-headed ants have been seen on the island for two years.
CSIRO, Author provided

A super colony

The ability to eradicate this ant is largely due to its relatively unique social organisation. The queens don’t fly to new locations to start new nests – instead, they form interconnected colonies that can extend over large areas.

This makes the ant’s distribution easy to map and treat. The ant requires human assistance for long-distance transport, so the ant will only be found in predictable locations where it can be accidentally transported by people.

From 2012 to 2015, all locations on the island where the ant was likely to be present were formally inspected. Priority was given to places where an infestation was previously recorded or considered likely. The populations were mapped, and then treated using a granular bait available at shops.

In the latter years we found 16 populations covering 30 hectares. Limited by poor mapping in the early years, we estimate that the ant originally covered up to 55 hectares, roughly 15% of the island.

Stopping the spread

The widespread distribution of the ant through the populated area of the island is thought to have been aided by the movement of infested mulch and other materials from the island’s Waste Management Facility.

To prevent any more spread of the ant, movement restrictions were imposed in 2003 on the collection of green waste, building materials and other high risk items from the facility.

The baiting program used a product that contains a very low dose of insecticide that has an extremely low toxicity to terrestrial vertebrates such as pet cats and dogs, birds, lizard etc. The toxicant rapidly breaks down into harmless chemicals after exposure to light.

No negative impacts were recorded on any of the native wildlife on the island.

Importantly, the African ant usually kills most other ants and other invertebrates where it is present, so there are few invertebrates present to be affected by the bait.

Ecological recovery of the infested areas was rapid following baiting and the eradication of the African ant.

Another ant invader

One of the main challenges was getting the ground crew to correctly identify the ant.

It turns out there was a second (un-named) big-headed ant species present, also not native to the island, that created a lot of unnecessary work being conducted where the African ant wasn’t present.

CSIRO and Lord Howe Island Board team tackling the African big headed ant problem.
CSIRO, Author provided

Like numerous other exotic ant species present, this second species was of no environmental or social concern, so there are no plans to manage or eradicate it.

The protocols used in this program are essentially the same that are being used in other eradication programs against Electric ant in Cairns and Browsing ant in Darwin and Perth, because those two species also create supercolonies.




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It is highly likely that those programs will also achieve eradication of their respective species, the first instance where an ant species has been eradicated entirely from Australia.

The fire ant program in Brisbane has many similarities, but there are distinct differences in that the ants there don’t form supercolonies that are so easy to map, and the area involved is far greater.The Conversation

Ben Hoffman, Principal research scientist, CSIRO

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The backflip over Sydney’s marine park is a defiance of science



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Sydney’s iconic beaches are not yet part of a marine park.
John Turnbull

David Booth, University of Technology Sydney and John Turnbull, UNSW

The New South Wales government’s decision to back away from establishing no-fishing zones in waters around Sydney leaves significant question marks over the plan, which is open for public consultation until September 27.

Fisheries Minister Niall Blair explained the apparent backflip by saying he was “confident that fishing is not the key threat to the sustainability of our marine environment”, after receiving what he described as “robust” feedback from local communities and anglers.

The original plans for Sydney’s marine park. Click image to enlarge.
NSW government

The originally proposed Sydney Marine Park comprised 17 “sanctuary zones” (totalling 2.4% of the area, including estuaries), 3 “conservation zones” totalling 2.6%, and 21 “special purpose zones”, which would allow (and in some cases protect) fishing.

Sanctuary zones allow no fishing; conservation zones allow taking of lobster and abalone (see below); and special purpose zones have a range of restrictions or allowances, not necessarily of any conservation benefit. For instance, four offshore artificial reefs are classed as special purpose zones.

The plans cover the waters around Sydney, stretching from Newcastle in the north to Wollongong in the south. Formally known as the Hawkesbury Shelf marine bioregion, it is the only bioregion wholly in NSW that does not have a marine park. This is despite Sydney’s magnificent array of underwater and coastal habitats, which are home to more fish species than the entire British Isles.




Read more:
Recreational fishing in marine parks: you can’t be serious!


New zones and ranked threats

The original marine park proposal was far from ideal. A good marine park should have a string of closely connected sanctuary zones, but there was a large gap from southern Sydney to Wollongong where no sanctuary zones were proposed.

Instead, there was a new “conservation zone” to allow fishing for lobster and abalone. Yet lobster in particular are important to this ecosystem, because they protect kelp by preying on sea urchins.

Threats to the marine region around Sydney, as ranked in a NSW government report. Click image to enlarge.
NSW government

The NSW government based its earlier proposal on a principle called TARA, short for “threat and risk assessment”, in which all perceived factors are ranked according to their environmental, social and economic outcomes.

While other major threats such as climate change and pollution are ranked highly, fishing doesn’t appear until number 18 on the government’s list (see page 8 here. One reason for this is that fishing is split into eight categories (such as “recreational fishing by boat – line and trap”), masking its overall impact. Even 4WDs on beaches are ranked as a greater threat to the environment than many types of fishing.

Premier Gladys Berejiklian’s press release about the marine park public consultation didn’t mention the environmental threat posed by fishing at all. Yet there is clear evidence that fishing directly harms fish stocks.

One recent study shows that stocks of inshore fish species have declined in Australia by 30% in a decade, except in sanctuary zones. Worldwide, sanctuary zones (also called no-take zones) have been shown to help fish grow larger and more abundant. And recent studies in NSW coastal waters have reiterated the benefits of no-take zones for species such as morwong, bream, and snapper.

Partial protection doesn’t work

The latest proposals, which would allow recreational but not commercial fishing, would be much less effective than full protection. One recent study suggested that partial protection is no better than no protection at all.

According to a NSW government estimate, recreational fishing removes more than 3 million fish, crustaceans and molluscs from NSW coastal waters every year. But marine parks are primarily about conservation, and this requires us to face some stark realities. With more than 8 million people likely to call Sydney home in the next 40 years, pressures on our coasts will only increase.

Sanctuary zones are one of the best available conservation tools to guard against these impacts. These zones have also been shown to make wildlife more resilient to climate change.

Even before the government’s decision to rescind the proposed sanctuary zones, the original plan for no-take zones to cover just 2.4% of the region was a severe compromise. By comparison, the Great Barrier Reef Marine Park has 30% sanctuary zone coverage, and the rest of NSW has 7-8%. International best practice recommends at least 20%, and even the Commonwealth Marine Reserves Management Plan offers 6% no-take coverage.

But now, with no sanctuary zones, Sydney’s proposed “marine park” is not worthy of the name.

Wrong priorities

A peculiar contradiction is that despite one-quarter of the listed threats being fishing-related, the NSW government’s marine estate management strategy includes an initiative to encourage fishing. Pollution is also a high-priority threat, and fishing is the largest source of subtidal debris.

Kelp and a tangle of discarded fishing line.
John Turnbull

If local-level threats such as fishing and litter are not dealt with, resilience to climate change suffers as a result. We must tackle all threats – overfishing, pollution, climate change – and not shy away from one because it’s politically unpalatable.




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Marine parks for fish and people: here’s how to do it


It is frustrating that the NSW government has opted to abolish these marine sanctuaries before the public consultation was complete. The wider public understands the value of sanctuary zones, as indicated in recent opinion polls showing clear support for the original plans among Sydneysiders – even many of those who fish.

Some fishers are now calling for sanctuary zones to be scrapped or wound back in other iconic NSW marine parks, such as Lord Howe Island and Solitary Islands. This move would be a defiance of the science. The evidence shows that sanctuary zones are essential for restoring and preserving our marine estate for future generations.The Conversation

David Booth, Professor of Marine Ecology, University of Technology Sydney and John Turnbull, , UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The Lord Howe screw pine is a self-watering island giant



File 20180824 149475 1045iq3.png?ixlib=rb 1.1
To grow tall enough to reach the canopy, a species of screw pine unique to Lord Howe Island has evolved its own rainwater harvesting system.
Matthew Biddick, CC BY-SA

Matthew Biddick, Victoria University of Wellington

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Pandanus forsteri, a species of screw pine endemic to Lord Howe Island, grows tall like no other tree on Earth. To reach the canopy, these trees have evolved a rainwater harvesting system that enables them to water themselves.

Originally from Micronesia, the palm-like P. forsteri belongs to a group of trees that have populated almost every coastal habitat of the Pacific. In fact, pandans are used by Oceanic cultures for everything from fishing and cooking to medicine and religious ceremonies.

Our research shows that pandans differ in several fundamental ways from more familiar trees, including how they capture water and grow.




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Reaching for the canopy

Most trees lay down concentric rings of vascular tissue as they mature, thickening over time. This enables them to grow tall, yet maintain enough structural integrity to avoid toppling over. It is also arguably the most important evolutionary innovation that has enabled trees to colonise most of terrestrial Earth.

Together with palms, bamboo and yucca, pandans belong to a group known as monocots, because their seedlings produce a single embryonic leaf.

Pandans belong to a group of plants whose vascular tissue is still primitive, making it difficult to grow tall.
Ian Hutton, CC BY-SA

Their vascular tissue is not compartmentalised in the same way. It forms bundles that are positioned somewhat haphazardly within the stem. Consequently, monocots are unable to produce true secondary growth and thicken like other trees do – and reaching the canopy becomes a much more ambitious endeavour.

The canopy offers a good life. The sun is shining, seed-dispersing birds are abundant, and the herbivores of the forest floor are a distant concern. In monocots, natural selection has favoured some inventive ways of stretching to the top.

Pay-as-you-go growth

Palms overcome the limitations imposed by their physiology by spending their younger years laying down enough vascular girth to support their future stature. Think of it like putting aside money for your retirement. You may not need it now, but you will likely later depend on it.

Stilt roots support the crown as it matures.
Kevin Burns, CC BY-SA

Once thick enough, palms shift their efforts to vertical growth. The palm’s tactic of delayed vertical growth may be slow, but it functions well enough to thrust Columbian wax palms (Ceroxylon quindiuense) – the world’s tallest monocot – 45 meters into the clouds.

Pandans, on the other hand, are less patient. Unlike palms, they prefer a sort of “pay-as-you-go” method. They produce stilt roots that extend from the trunk to the ground for support as the crown matures. The end result gives the appearance of an ice cream cone perched on a tepee of stilts. It’s an odd strategy, but it works.

However, on Lord Howe Island, something quite remarkable has transpired. Isolated some 600 kilometres off the east coast of Australia, one species of screw pine has evolved into an island giant.

Lord Howe Island, some 600km off the Australian east coast, is home to countless endemic plants and animals.
Ian Hutton, CC BY-SA

Island syndrome

Most screw pines are lucky to reach four or five meters. Pandanus forsteri trees, however, regularly exceed 15 meters. These kinds of size changes are not uncommon on isolated islands. They are part of a repeated evolutionary phenomenon known as the island syndrome.

Species on isolated islands are free from the stressors of continental life, and they subsequently converge on a more optimal, ancestral form. Large continental species evolve into island dwarfs, while smaller species become comparatively gigantic. Support for the island syndrome primarily comes from animals. However, a growing body of evidence suggests island plants follow a similar evolutionary path.




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A network of aqueducts on the root surface guides water to the absorptive tissue at the tip of the growing root.
Matt Biddick, CC BY-SA

While gigantism may be favourable, it doesn’t come without risks – and for P. forsteri, they are serious. Thanks to their new-found stature, P. forsteri trees must produce enormous stilt roots to support themselves. This process that can take years. Exposed to the air, roots can form air bubbles, and an air bubble in a plant is bad in the same way it is bad in your artery. It is potentially lethal.

Nature appears to have solved this problem through the evolution of a rainwater harvesting system that enables P. forsteri to water its own stilt roots before they reach the ground.

Gutter-like leaves collect rainwater and transport it to the trunk, where it descends. The flow of water is then couriered by a network of aqueducts formed by the root surface. Finally, water is stored in a specialised organ of absorptive tissue encasing the growing root tip.

Back to the drawing board

This is dramatically different from how we traditionally think about plants. It is far from our concept of sessile beings that passively absorb everything they need from the soil, thanks to the capillary action of their vascular tissues. Never before has a plant species been shown to possess a system of traits that operate jointly to capture, transport and store water external to itself.

This species has opened our eyes to an entirely new field of scientific inquiry. It forces scientists to rethink the function of organs like leaves and roots outside of the contexts of photosynthesis and the conduction of soil water.

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The Conversation

Do other plants harvest rainwater in this way? Why have we only just discovered this? Has our overly simplistic view of plants hindered our ability to comprehend their true complexity? Only time, and more research, will tell.

Matthew Biddick, PhD Researcher, Victoria University of Wellington

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