Under the moonlight: a little light and shade helps larval fish to grow at night



Jeffrey Shima, Author provided

Jeffrey Shima, Te Herenga Waka — Victoria University of Wellington; Craig W. Osenberg, University of Georgia; Stephen Swearer, The University of Melbourne, and Suzanne Alonzo, University of California, Santa Cruz

At night on any one of hundreds of coral reefs across the tropical Pacific, larval fish just below the sea surface are gambling on their chances of survival.

Our latest research shows the brightness of the Moon could play a major role in that struggle for survival by affecting the availability of prey and keeping predators away.

Understanding how that works could help in fisheries management, specifically the prediction of changes to harvested fish stocks that allow us to anticipate how many adult fish can be taken without destabilising the fishery.

Many fish populations experience boom-and-bust cycles largely because parents routinely produce millions of offspring that have very low, but fluctuating, survival rates.

The large number of larval fish that are produced means any environmental conditions — for example, increased nutrients — that improve survival odds even only marginally can lead to a big influx in the number of surviving offspring.

Several sixbar wrasse swim above a reef.
Adult sixbar wrasse in courtship.
Author?, Author provided

When the Sun goes down

In the past we failed to take into account the influences the night may have on fish development.

In our research we found the daily growth rates of the larvae of sixbar wrasse (Thalassoma hardwicke) around the island of Mo’orea, in French Polynesia, are strongly linked to phases of the Moon.




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Their growth appears to be maximised when the first half of the night is dark and the second half of the night is bright.

Cloudy nights obscure the Moon, and thus allowed us to check our models by contrasting growth on cloudy versus clear nights, which confirmed the effect of moonlight on growth of these fish.

Phases of the Moon

We found that on the best nights of the lunar month for sixbars, around the last Quarter Moon when the Moon rises around midnight, larval fish grew about 0.012mm a day more than average.

But on the worst nights, around the first Quarter Moon when the Moon is overhead at sunset and sets around midnight, they grew about 0.014mm a day less than average.

From First Quarter to Full Moon then Last Quarter.
Phases of the Moon from the Southern Hemisphere.
Wikimedia, CC BY-SA

For a typical larval sixbar of 37.5 days old, that means its growth is 24% more on the best night than on the worst one. This is important, as growth is inextricably linked to survival and ultimately fisheries productivity.

We think the Moon affects larval growth in this way because of how it changes the movements of deeper-dwelling animals, those that migrate into shallow water each night to hunt for food under the cover of darkness.

Zooplankton — potential prey for larval sixbars — respond quickly to the arrival of darkness, and move into the surface water to supplement the diets of sixbars.

Micronekton, such as lanternfishes, which hunt larval fishes, may take much longer to reach surface waters and seek out their prey, due to their migration from much deeper depths.

Four graphs showing different phases of the Moon and the amount of predator/prey during each phase.
Four graphs showing the larval fish (in yellow) and the amount of predator (red shading area) and prey (brown shading area) rising to the surface during each phase of he Moon.
Proceedings of the Royal Society B, Author provided

As a consequence, prey availability for sixbars in surface waters may be hindered by early nocturnal brightness while the arrival of predators may be impeded by late nocturnal brightness.

Thus, larval fish grow best when their predators are absent but their prey are abundant — around the last Quarter Moon.

In contrast, around the first Quarter Moon, prey are suppressed but predators are not, leading to the slowest growth.

During the New Moon, when the surface waters remain dark throughout the night, influxes of both prey and predators may be high, with the latter preventing the larval fish from enjoying the increased numbers of prey.

On the other hand, during the Full Moon, when surface waters are well-lit, the movement of prey and predators may be suppressed, reducing the risk to the fish but also eliminating their food.

Impact on fishing

More research is needed to quantify these lunar effects on other marine populations. But our findings to date are good news for those working to strengthen fisheries management, given that phases of the Moon are predictable and cloud cover that can modify moonlight is being measured by satellites.

A diver underwater keeping watch on one of the sixbar wrasse fish.
Observing the sixbar wrasse spawning.
Author?, Author provided

This makes the incorporation of moonlight into existing fisheries management models relatively simple.

We think this will have implications around the world, not just in the tropics. This is because the nightly upward movements of deep-water animals is ubiquitous — it is the largest mass migration of biomass on the planet, and it happens everywhere.

The suppressive effect of moonlight on this movement of potential predators and prey is also a global phenomenon.

We evaluated effects of the Moon on growth of larval temperate fish in an earlier study and found a similar effect (moonlight enhanced growth).




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The effect is stronger and more nuanced in our latest study, most likely because the waters in the tropics are comparatively clear.

Our findings also hint that other factors which affect night-time illumination of the sea may disrupt marine ecosystems. This includes the reflection of artificial lights from coastal cities, suspended sediments in the water column, and changes in cloud cover due to climate change.

In the future, we may be able to harness this extra information to help forecast fish population change to better guide the management and conservation of fisheries around the world.The Conversation

Jeffrey Shima, Professor of Ecology, Te Herenga Waka — Victoria University of Wellington; Craig W. Osenberg, Professor of Ecology, University of Georgia; Stephen Swearer, Professor of Marine biology, The University of Melbourne, and Suzanne Alonzo, Professor of Ecology & Evolutionary Biology, University of California, Santa Cruz

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

To fix Australia’s environment laws, wildlife experts call for these 4 changes — all are crucial



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Don Driscoll, Deakin University; April Reside, The University of Queensland; Brendan Wintle, The University of Melbourne; Euan Ritchie, Deakin University, and Martine Maron, The University of Queensland

The independent review of Australia’s main environment law, released last week, provided a sobering but accurate appraisal of a dire situation.

The review was led by Professor Graeme Samuel and involved consultation with scientists, legal experts, industry and conservation organisations. Samuel’s report concluded Australia’s biodiversity is in decline and the law (the EPBC Act) “is not fit for current or future environmental challenges”.

The findings are no surprise to us. As ecologists, we’ve seen first hand how Australia’s nature laws and governance failure have permitted environmental degradation and destruction to the point that species face extinction. Even then, continued damage is routinely permitted.

And the findings aren’t news to many other Australians, who have watched wildlife and iconic places such as Kakadu and Kosciuszko national parks, and the Great Barrier Reef, decline at rates that have only accelerated since the act was introduced in 1999. Even globally recognisable wildlife, such as the platypus, now face a future that’s far from certain.

To reverse Australia’s appalling track record of protecting biodiversity, four major reforms recommended by Samuel must be implemented as a package.

1. Setting standards

One of the many failings of Australia’s environmental laws is there has never been a point beyond which no further impacts are acceptable.

The government almost never says “enough!”, whether it’s undermining wetlands for a new mine, or clearing woodlands for agriculture. Species continue to suffer death by a thousand cuts.




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For example, the original distribution of the endangered southern black-throated finch of southern and central Queensland has shrunk to less than 10% due to land clearing and habitat degradation. Yet, further clearing was approved for coal mines, housing developments and sugar cane farms.

Biodiversity offsets, which aim to compensate for environmental damage by improving nature elsewhere, have for the most part been dreadfully ineffective. Instead they have been a tool to facilitate biodiversity loss.

Two black-throated finches on a branch, one flying, against a blue sky.
Land clearing and cattle grazing are among the threats black-throated finches face.
Stephanie Todd, Author provided

The centre piece of Samuel’s report are proposed new National Environmental Standards. These would provide clear grounds for drawing a line in the sand on environmental damage.

Legal, rigorous enforcement of these standards could turn around Australia’s centuries-long record of destroying its natural heritage, and curb Australia’s appalling extinction rate — while also providing clarity and certainty for business.

Vital features of the standards Samuel recommends include:

  • avoiding impacts on the critical habitat of threatened species

  • avoiding impacts that could reduce the abundance of threatened species with already small and declining populations

  • no net reduction in the population size of critically endangered and endangered species

  • cumulative impacts must be explicitly considered for threatened species and communities

  • offsets can only be used as a last resort, not as a routine part of business like they are at the moment.

Under the proposed National Environmental Standards, any new developments would need to be in places where environmental damage is avoided from the outset, with offsets only available if they’re ecologically feasible and effective.

2. Greater government accountability

The federal environment minister can make decisions with little requirement to publicly justify them.

In 2014, then environment minister Greg Hunt controversially approved an exemption to the EPBC Act for Western Australia’s shark cull. This was despite evidence the cull wouldn’t make people safer, would harm threatened species and would degrade marine ecosystems. Hunt could shirk the evidence, deny the impacts and make a politically expedient decision, with no mechanisms in place to call him to account.

Tiger shark swimming near the sea bed
Tiger sharks and white sharks were targeted in the WA cull.
Shutterstock

Samuel’s report states the minister can make decisions that aren’t consistent with the National Environmental Standards — but only as a “rare exception”. He says these exceptions must be “demonstrably justified in the public interest”, and this justification must be published.




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We think this epitomises democracy. Ministers can make decisions, but they must be open to public and robust scrutiny and explain how their decisions might affect environments and species.

Improved accountability will be one of the many benefits of Samuel’s proposed independent Environment Assurance Commissioner, which would be backed up by an Office of Compliance and Enforcement. Samuel says these must be free from political interference.

These are absolutely critical aspects of the reforms. Standards that aren’t audited or enforced are as worthless as an unfunded recovery plan.

3. Decent funding

Samuel urges improved resourcing because to date, funding to protect species and the environment has been grossly inadequate. For example, experts recently concluded up to 11 reptile species are at risk of extinction in the next 50 years in Australia, and limited funding is a key barrier to taking action.

A small lizard sitting on a human hand
Victoria’s grassland earless dragon (Tympanocryptis pinguicolla) is one of 11 reptile species identified as at risk of extinction.
Michael Mulvaney/Wikimedia, CC BY-SA

And it has been proven time and again that lack of action due to under-resourcing leads to extinction. The recent extinction of the Christmas Island forest skink, the Christmas Island pipistrelle, and the Bramble Cay melomys were all attributable, in large part, to limited funding, both in the administration of the threatened species listing process, and in delivering urgent on-ground action.




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We need only look to the COVID pandemic to know when faced with emergencies, the government can rapidly deploy substantial sums of money for urgent interventions. And we are well and truly in an environmental emergency.

Spending to care for the environment is not a cost that delivers no return. It’s an investment that delivers substantial benefits, from creating jobs to cleaner water and healthier people.

4. Increase ecological knowledge

Engaging experts is key to achieving Samuel’s long-overdue proposed reforms. He calls for the immediate creation of expert committees on sustainable development, Indigenous participation, conservation science, heritage, and water resources. This will help support the best available data collection to underpin important decisions.

Ultimately, though, much more investment in building ecological knowledge is required.

Australia has more than 1,900 listed threatened species and ecological communities, and most don’t even have active recovery plans. Ecologists will need to collect, analyse and interpret new, up-to-date data to make biodiversity conservation laws operational for most threatened species.

For example, while we know logging and fires threaten greater gliders, there’s still no recovery plan for this iconic forest possum. And recent research suggests there are actually three — not simply one — species of greater glider. Suspected interactions between climate change, fire and logging, and unexplained severe population declines, means significant new effort must be invested to set out a clear plan for their recovery.




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Samuel recommends Regional Recovery Plans be adequately funded to help develop some knowledge. But we suggest substantial new environmental capacity is needed, including new ecological research positions, increased environmental monitoring infrastructure, and appropriate funding of recovery plans, to ensure enough knowledge supports decision making.

Cherry picking recommendations condemns our species

Samuel’s report has provided a path forward that could make a substantial difference to Australia’s shocking track record of biodiversity conservation and land stewardship.

But Environment Minister Sussan Ley’s response so far suggests the Morrison government plans to cherry pick from Samuel’s recommendations, and rush through changes without appropriate safeguards.

If the changes we outlined above aren’t implemented as a package, our precious natural heritage will continue to decline.




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The Conversation


Don Driscoll, Professor in Terrestrial Ecology, Deakin University; April Reside, Researcher, Centre for Biodiversity and Conservation Science, The University of Queensland; Brendan Wintle, Professor in Conservation Ecology, School of BioSciences, The University of Melbourne; Euan Ritchie, Professor in Wildlife Ecology and Conservation, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, and Martine Maron, ARC Future Fellow and Professor of Environmental Management, The University of Queensland

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

Taking care of business: the private sector is waking up to nature’s value



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Megan C Evans, UNSW

For many businesses, climate change is an existential threat. Extreme weather can disrupt operations and supply chains, spelling disaster for both small vendors and global corporations. It also leaves investment firms dangerously exposed.

Businesses increasingly recognise climate change as a significant financial risk. Awareness of nature-related financial risks, such as biodiversity loss, is still emerging.

My work examines the growth of private sector investment in biodiversity and natural capital. I believe now is a good time to consider questions such as: what are businesses doing, and not doing, about climate change and environmental destruction? And what role should government play?

Research clearly shows humanity is severely damaging Earth’s ability to support life. But there is hope, including a change in government in the United States, which has brought new momentum to tackling the world’s environmental problems.

Koala lies dead after a bushfire tears through forest
Now’s a good time to talk about how humans are wrecking the planet.
Daniel Mariuz/AAP

Poisoning the well

An expert report released last week warned Australia must cut emissions by 50% or more in the next decade if it’s to meet the Paris Agreement goals. Meeting this challenge will require everyone to do their bit.

Climate change is a major threat to Australia’s financial security, and businesses must be among those leading on emissions reduction. Unfortunately, that’s often not the case.

The finance sector, for example, contributes substantially to climate change and biodiversity loss. It does this by providing loans, insurance or investment for business activities that produce greenhouse gas emissions or otherwise harm nature.

In fact, a report last year found Australia’s big four banks loaned A$7 billion to 33 fossil fuel projects in the three years to 2019.

Protest banner on coal pile at terminal
Australia’s big banks have been criticised for investing in fossil fuels.
Dean Sewell/Greenpeace

A pushback for nature

Promisingly, there’s a growing push from some businesses, including in the finance sector, to protect the climate and nature.

Late last year, Australian banks and insurers published the nation’s first comprehensive climate change reporting framework. And the recently launched Climate League 2030 initiative, representing 17 of Australia’s institutional investors with A$890 billion in combined assets, aims to act on deeper emissions reductions.




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Some companies are starting to put serious money on the table.
In August last year, global financial services giant HSBC and climate change advisory firm Pollination announced a joint asset management venture focused on “natural capital”. The venture aims to raise up to A$1 billion for its first fund.

Globally too, investors are starting to wake up to the cost of nature loss. Last month, investors representing US$2.4 trillion (A$3.14 trillion) in assets asked HSBC to set emissions reduction targets in line with the Paris Agreement. And in September last year, investor groups worth over $US103 trillion (A$135 trillion) issued a global call for companies to accurately disclose climate risks in financial reporting.

HSBC sign lit at night
HSBC’s investors are pushing for stronger climate action.
Shutterstock

Climate change is not the only threat to global financial security. Nature loss – the destruction of plants, animals and ecosystems – poses another existential threat. Last year, the World Economic Forum reported more than half of the global economy relies on goods and services nature provides such as pollination, water and disease control.

Efforts by the finance sector to address the risks associated with biodiversity loss are in their infancy, but will benefit from work already done on understanding climate risk

Of course, acknowledging and disclosing climate- and nature-related financial risks is just one step. Substantial action is also needed.

Businesses can merely “greenwash” their image – presenting to the public as environmentally responsible while acting otherwise. For example, a report showed in 2019, many major global banks that pledged action on climate change and biodiversity loss were also investing in activities harmful to biodiversity.

Logs felled in timber operation
The global economy depends on the goods and services nature provides.
Shutterstock

Getting it right

In the financial sector and beyond, there are risks to consider as the private sector takes a larger role in environmental action.

Investors will increasingly seek to direct capital to projects that help to reduce their exposure to climate- and nature-related risks, such ecosystem restoration and sustainable agriculture.

Many of these projects can help to restore biodiversity, sequester carbon and deliver benefits for local communities. But it’s crucial to remember that private sector investment is motivated, at least in part, by the expectation of a positive financial return.

Projects that are highly risky or slow to mature, such as restoring highly threatened species or ecosystems, might struggle to attract finance. For example, the federal government’s Threatened Species prospectus reportedly attracted little private sector interest.

That means governments and philanthropic donors still have a crucial role in the funding of research and pilot projects.




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Governments must also better align policies to improve business and investor confidence. It is nonsensical that various Australian governments send competing signals about whether, say, forests should be cleared or restored. And at the federal level, biodiversity loss and climate change come under separate portfolios, despite the issues being inextricably linked.

Private-sector investment could deliver huge benefits for the environment, but these outcomes must be real and clearly demonstrated. Investors want the benefits measured and reported, but good data is often lacking.

Too-simple metrics, such as the area of land protected, don’t tell the whole story. They may not reflect harm to local and Indigenous communities, or whether the land is well managed.

Finally, as the private sector becomes more aware of nature and climate-related risks, a range of approaches to addressing this will proliferate. But efforts must be harmonised to minimise confusion and complexity in the marketplace. Governments must provide leadership to make this a smooth process.

Swift parrot flies through treetops
Threatened species habitat restoration may struggle to attract private sector funding.
Eric Woehler

The power to change

Last week, a major report was released highlighting grave failures in Australia’s environmental laws. The government’s response suggested it is not taking the threat seriously.

Businesses and governments hold disproportionate power that can be used to either delay or accelerate transformative change.

And although many businesses wield undue influence on government decisions, it doesn’t have to be this way.

By working together and seizing the many opportunities that present, business and government can help arrest climate change and nature loss, and contribute to a safer, more liveable planet for all.




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The Conversation


Megan C Evans, Lecturer and ARC DECRA Fellow, UNSW

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