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.

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.

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 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.

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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Coral reefs: climate change and pesticides could conspire to crash fish populations

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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.

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.

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Yes, more carbon dioxide in the atmosphere helps plants grow, but it’s no excuse to downplay climate change

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Vanessa Haverd, CSIRO; Benjamin Smith, Western Sydney University; Matthias Cuntz, Université de Lorraine, and Pep Canadell, CSIRO

The alarming rate of carbon dioxide flowing into our atmosphere is affecting plant life in interesting ways – but perhaps not in the way you’d expect.

Despite large losses of vegetation to land clearing, drought and wildfires, carbon dioxide is absorbed and stored in vegetation and soils at a growing rate.

This is called the “land carbon sink”, a term describing how vegetation and soils around the world absorb more carbon dioxide from photosynthesis than they release. And over the past 50 years, the sink (the difference between uptake and release of carbon dioxide by those plants) has been increasing, absorbing at least a quarter of human emissions in an average year.

The sink is getting larger because of a rapid increase in plant photosynthesis, and our new research shows rising carbon dioxide concentrations largely drive this increase.

So, to put it simply, humans are producing more carbon dioxide. This carbon dioxide is causing more plant growth, and a higher capacity to suck up carbon dioxide. This process is called the “carbon dioxide fertilisation effect” – a phenomenon when carbon emissions boost photosynthesis and, in turn, plant growth.

What we didn’t know until our study is just how much the carbon dioxide fertilisation effect contributes to the increase in global photosynthesis on land.

But don’t get confused, our discovery doesn’t mean emitting carbon dioxide is a good thing and we should pump out more carbon dioxide, or that land-based ecosystems are removing more carbon dioxide emissions than we previously thought (we already know how much this is from scientific measurements).

And it definitely doesn’t mean mean we should, as climate sceptics have done, use the concept of carbon dioxide fertilisation to downplay the severity of climate change.

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Read more:
How to design a forest fit to heal the planet

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Rather, our findings provide a new and clearer explanation of what causes vegetation around the world to absorb more carbon than it releases.

What’s more, we highlight the capacity of vegetation to absorb a proportion of human emissions, slowing the rate of climate change. This underscores the urgency to protect and restore terrestrial ecosystems like forests, savannas and grasslands and secure their carbon stocks.

And while more carbon dioxide in the atmosphere does allow landscapes to absorb more carbon dioxide, almost half (44%) of our emissions remain in the atmosphere.

More carbon dioxide makes plants more efficient

Since the beginning of the last century, photosynthesis on a global scale has increased in nearly constant proportion to the rise in atmospheric carbon dioxide. Both are now around 30% higher than in the 19th century, before industrialisation began to generate significant emissions.

Carbon dioxide fertilisation is responsible for at least 80% of this increase in photosynthesis. Most of the rest is attributed to a longer growing season in the rapidly warming boreal forest and Arctic.

Ecosystems such as forests act as a natural weapon against climate change by absorbing carbon from the atmosphere.
Shutterstock

So how does more carbon dioxide lead to more plant growth anyway?

Higher concentrations of carbon dioxide make plants more productive because photosynthesis relies on using the sun’s energy to synthesise sugar out of carbon dioxide and water. Plants and ecosystems use the sugar both as an energy source and as the basic building block for growth.

When the concentration of carbon dioxide in the air outside a plant leaf goes up, it can be taken up faster, super-charging the rate of photosynthesis.

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CO₂ levels and climate change: is there really a controversy?

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More carbon dioxide also means water savings for plants. More carbon dioxide available means pores on the surface of plant leaves regulating evaporation (called the stomata) can close slightly. They still absorb the same amount or more of carbon dioxide, but lose less water.

The resulting water savings can benefit vegetation in semi-arid landscapes that dominate much of Australia.

We saw this happen in a 2013 study, which analysed satellite data measuring changes in the overall greenness of Australia. It showed more leaf area in places where the amount of rain hadn’t changed over time. This suggests water efficiency of plants increases in a carbon dioxide-richer world.

Young forests help to capture carbon dioxide

In other research published recently, we mapped the carbon uptake of forests of different ages around the world. We showed forests regrowing on abandoned agricultural land occupy a larger area, and draw down even more carbon dioxide than old-growth forests, globally. But why?

Young forests need carbon to grow, so they’re a significant contributor to the carbon sink.
Shutterstock

In a mature forest, the death of old trees balances the amount of new wood grown each year. The old trees lose their wood to the soil and, eventually, to the atmosphere through decomposition.

A regrowing forest, on the other hand, is still accumulating wood, and that means it can act as a considerable sink for carbon until tree mortality and decomposition catch up with the rate of growth.

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This age effect is superimposed on the carbon dioxide fertilisation effect, making young forests potentially very strong sinks.

In fact, globally, we found such regrowing forests are responsible for around 60% of the total carbon dioxide removal by forests overall. Their expansion by reforestation should be encouraged.

Forests are important to society for so many reasons – biodiversity, mental health, recreation, water resources. By absorbing emissions they are also part of our available arsenal to combat climate change. It’s vital we protect them.

Vanessa Haverd, Principal research scientist, CSIRO; Benjamin Smith, Director of Research, Hawkesbury Institute for the Environment, Western Sydney University; Matthias Cuntz, Research Director INRAE, Université de Lorraine, and Pep Canadell, Chief research scientist, CSIRO Oceans and Atmosphere; and Executive Director, Global Carbon Project, CSIRO

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

Climate explained: regenerative farming can help grow food with less impact

Returning nutrients, including animal feces, to the land is important to maintain the soil’s capacity to sequester carbon.
from http://www.shutterstock.com, CC BY-ND

Troy Baisden, University of Waikato

CC BY-ND

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

I would like to know to what extent regenerative agriculture practices could play a role in reducing carbon emissions and producing food, including meat, in the future. From what I have read it seems to offer much, but I am curious about how much difference it would make if all of our farmers moved to this kind of land management practice. Or even most of them. – a question from Virginia

To identify and quantify the potential of regenerative agriculture to reduce greenhouse gas emissions, we first have to define what it means. If regenerative practices maintain or improve production, and reduce wasteful losses on the farm, then the answer tends to be yes. But to what degree is it better, and can we verify this yet?

Let’s first define how regenerative farming differs from other ways of farming. For example, North Americans listening to environmentally conscious media would be likely to define most of New Zealand pastoral agriculture systems as regenerative, when compared to the tilled fields of crops they see across most of their continent.

If milk and meat-producing animals are not farmed on pasture, farmers have to grow grains to feed them and transport the fodder to the animals, often over long distances. It’s hard to miss that the transport is inefficient, but easier to miss that nutrients excreted by the animals as manure or urine can’t go back to the land that fed them.

Healthy soils

Returning nutrients to the land really matters because these build up soil, and grow more plants. We can’t sequester carbon in soil without returning nutrients to the soil.

New Zealand’s style of pastoral agricultural does this well, and we’re still improving as we focus on reducing nutrient losses to water.

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Our pastoral soils tend to have as much carbon as they once did under forest, but concerns have been raised about carbon losses in some regions. Yet, we do still have two big problems.

First, the animals that efficiently digest tough plants – including cows, sheep, and goats – all belch the greenhouse gas methane. This is a direct result of their special stomachs, and chewing their cud. Therefore, farms will continue to have high greenhouse gas emissions per unit of meat and milk they produce. The recent Intergovernmental Panel on Climate Change (IPCC) report emphasised this, noting that changing diets can reduce emissions.

The second problem is worst in dairying. When a cow lifts its tail to urinate, litres of urine saturate a small area. The nitrogen content in this patch exceeds what plants and soil can retain, and the excess is lost to water as nitrate and to the air, partly as the powerful, long-lived greenhouse gas nitrous oxide.

Defining regenerative

Regenerative agriculture lacks a clear definition, but there is an opportunity for innovation around its core concept, which is a more circular economy. This means taking steps to reduce or recover losses, including those of nutrients and greenhouse gases.

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Regenerative agriculture can make farmers stewards of the land again

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Organic agriculture, which prohibits the use of antibiotics and synthetic pesticides and fertilisers, could potentially include regenerative agriculture. Organics once had the same innovative status, but now has a clear business model and supply chain linked to a price premium achieved through certification.

The price premium and regulation linked to certification can limit the redesign of the organic agricultural systems to incremental improvements, limiting the inclusion of regenerative concepts. It also means that emission studies of organic agriculture may not reveal the potential benefits of regenerative agriculture.

Instead, the potential for a redesign of New Zealand’s style of pastoral dairy farming around regenerative principles provides a useful example of how progress might work. Pastures could shift from ryegrass and clover to a more diverse, more deeply rooted mix of alternate species such as chicory, plantains, lupins and other grasses. This system change would have three main benefits.

Win-win-win

The first big win in farming is always enhanced production, and this is possible by better matching the ideal diet for cows. High performance ryegrass-clover pastures contain too little energy and too much protein. Diverse pastures fix this, allowing potential increases in production.

A second benefit will result when protein content of pasture doesn’t exceed what cows need to produce milk, reducing or diluting the nitrogen concentrated in the urine patches that are a main source of nitrous oxide emissions and impacts on water.

A third set of gains can result if the new, more diverse pastures are better at capturing and storing nutrients in soil, usually through deeper and more vigorous root growth. These three gains interrelate and create options for redesign of the farm system. This is best done by farmers, although models may help put the three pieces together into a win-win-win.

Whether you’re interested in local beef in Virginia, or the future of New Zealand’s dairy industry, the principles that define regenerative agriculture look promising for redesigning farming to reduce emissions. They may prove simpler than agriculture’s wider search for new ways of reducing greenhouse gas emissions, including genetically engineering ryegrass.

Troy Baisden, Professor and Chair in Lake and Freshwater Sciences, University of Waikato

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

Climate explained: why plants don’t simply grow faster with more carbon dioxide in air

Fast-growing plantation trees store less carbon per surface area than old, undisturbed forests that may show little growth.
from http://www.shutterstock.com, CC BY-ND

Sebastian Leuzinger, Auckland University of Technology

CC BY-ND

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

Carbon dioxide is a fertiliser for plants, so if its concentration increases in the atmosphere then plants will grow better. So what is the problem? – a question from Doug in Lower Hutt

Rising atmospheric carbon dioxide (CO₂) is warming our climate, but it also affects plants directly.

A tree planted in the 1850s will have seen its diet (in terms of atmospheric carbon dioxide) double from its early days to the middle of our century. More CO₂ generally leads to higher rates of photosynthesis and less water consumption in plants. So, at first sight, it seems that CO₂ can only be beneficial for our plants.

But things are a lot more complex than that. Higher levels of photosynthesis don’t necessarily lead to more biomass production, let alone to more carbon dioxide sequestration. At night, plants release CO₂ just like animals or humans, and if those respiration rates increase simultaneously, the turnover of carbon increases, but the carbon stock doesn’t. You can think of this like a bank account – if you earn more but also spend more, you’re not becoming any richer.

Even if plants grow more and faster, some studies show there is a risk for them to have shorter lifespans. This again can have negative effects on the carbon locked away in biomass and soils. In fact, fast-growing trees (e.g. plantation forests) store a lot less carbon per surface area than old, undisturbed forests that show very little growth. Another example shows that plants in the deep shade may profit from higher levels of CO₂, leading to more vigorous growth of vines, faster turnover, and, again, less carbon stored per surface area.

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Water savings

The effect of CO₂ on the amount of water plants use may be more important than the primary effect on photosynthesis. Plants tend to close their leaf pores slightly under elevated levels of CO₂, leading to water savings. In certain (dry) areas, this may indeed lead to more plant growth.

But again, things are much more complex and we don’t always see positive responses. Research we published in Nature Plants this year on grasslands around the globe showed that while dry sites can profit from more CO₂, there are complex interactions with rainfall. Depending on when the rain falls, some sites show zero or even negative effects in terms of biomass production.

Currently, a net amount of three gigatons of carbon are thought to be removed from the atmosphere by plants every year. This stands against over 11 gigatons of human-induced release of CO₂. It is also unclear what fraction of the three gigatons plants are taking up due to rising levels of CO₂.

In summary, rising CO₂ is certainly not bad for plants, and if we restored forested land at a global scale, we could help capture additional atmospheric carbon dioxide. But such simulations are optimistic and rely on conversion of much needed agricultural land to forests. Reductions in our emissions are unavoidable, and we have very strong evidence that plants alone will not be able to solve our CO₂ problem.

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Exaggerating how much CO₂ can be absorbed by tree planting risks deterring crucial climate action

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Sebastian Leuzinger, Associate Professor, Auckland University of Technology

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

Cities can grow without wrecking reefs and oceans. Here’s how

Cairns has lots of hard grey infrastructure but much less green infrastructure that would reduce the impacts of the city’s growth.
Karine Dupré, Author provided

Silvia Tavares, James Cook University and Karine Dupré, Griffith University

“What happens if the water temperature rises by a few degrees?” is the 2018 International Year of the Reef leading question. While the ocean is the focus, urbanisation is the main reason for the rising temperatures and water pollution. Yet it receives little attention in this discussion.

In turn, rising temperatures increase downpours and urban floods, adding to the pressures on urban infrastructure.

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Protecting the reef as Cairns grows

Cairns is an expanding Queensland city located between two World Heritage sites – the Great Barrier Reef and the Daintree Rainforest. While important research focuses on these sites themselves, not much is known about how the surrounding urban areas influence these natural environments. Similarly, little is known about how urban planning and design contribute to the health of the inner city and surrounding water bodies, including the ocean.

Cairns is a major Australian tourism destination with a unique coastal setting of rainforest and reef. This attracts growing numbers of visitors. One effect of this success is increased urbanisation to accommodate these tourists.

There are many opportunities to promote sustainable and socially acceptable growth in Cairns. Yet this growth is not without challenges. These include:

• impacts of climate change, including sea-level rise and ocean warming
• lack of comprehensive urban infrastructure strategy
• lack of comprehensive assessment of the benefits of integrated urban design to maximise coastal resilience and the health of streams and oceans.

Rain gardens are common in Singapore.
Roger Soh/Flickr, CC BY-SA

As with most Australian cities, Cairns has an urban layout based on wide streets, mostly with little or no greenery. Rain gardens, for instance, are rare. Bioswales that slow and filter stormwater are present along highways, but seldom within the city.

The arguments for not adding greenery to the urban environment are familiar. These typically relate to costs of implementation and maintenance, but also to the speed with which water is taken out of streets during the tropical rainy season. This is because green stormwater solutions, if not well planned, can slow down the water flow, thus increasing floods.

However, cities can be designed in a way to imitate nature with solutions that are an integral part of the urban system. This can include dedicated areas of larger wetlands and parks, which capture water and filter pollution and undesired nutrients more efficiently, reducing polluted runoff to the reef.

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If planners understand it’s cool to green cities, what’s stopping them?

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Integrated urban design

Integrated urban design is an aspect of city planning and design that could be further developed to ensure the whole system works more efficiently. This involves integrating the three elements that make up urban infrastructure:

1. the green – parks, residential gardens, rain gardens, green roofs and walls, bioswales, etc
2. the grey – built drains, footpaths, buildings, underground vacuum
   system, etc
3. the blue – streams, stormwater systems, etc.

A rain garden, which absorbs rain and stores water to help control run-off from impervious hard surfaces, in Wellington, New Zealand.
Karine Dupré

Urban infrastructure, therefore, can and should be planned and designed to provide multiple services, including coastal resilience and healthier water streams and oceans. To achieve this, a neighbourhood or city-wide strategy needs to be implemented, instead of intermittent and ad hoc urban design solutions. Importantly, each element should coordinate with the others to avoid overlaps, gaps and pitfalls.

This is what integrated urban design is about. So why don’t we implement it more often?

Challenges and opportunities

Research has shown that planning, designing and creating climate-resilient cities that are energy-optimised, revitalise urban landscapes and restore and support ecosystem services is a major challenge at the planning scale. To generate an urban environment that promotes urban protection and resilience while minimising urbanisation impacts and restoring natural systems, we need to better anticipate the risks and have the means to take actions. In other words, it is a two-way system: well planned and designed green and blue infrastructures not only deliver better urbanised areas but will also protect the ocean from pollution. Additionally, it helps to manage future risks of severe weather.

The uncertainties of green infrastructure capacity and costs of maintenance, combined with inflexible finance schemes, are obstacles to integrated urban solutions. Furthermore, the lack of inter- and transdisciplinary approaches results in disciplinary barriers in research and policymaking to long-term planning of the sort that generates urban green infrastructure and its desired outcomes.

On the bright side, there is also strong evidence to suggest sound policy can help overcome these barriers through technical guides based on scientific research, standards and financial incentives.

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Read more:
Here’s how green infrastructure can easily be added to the urban planning toolkit

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Collaborative partnerships are promising, too. Partnerships between academia and industry tend to be more powerful than streamlined industry project developments.

Finally, and very promisingly, Australia has its own successful green infrastructure examples. Melbourne’s urban forest strategy has been internationally acclaimed. Examples like these provide valuable insights into local green infrastructure governance.

Cairns has stepped up with some stunning blue infrastructure on the Esplanade which raises awareness of both locals and visitors about the protection of our oceans.

This is only the start. Together academics, local authorities, industry stakeholders and communities can lead the way to resilient cities and healthier oceans.

Cairns Esplanade Lagoon helps raise awareness of the need to protect the ocean as the city grows.
Karine Dupré, Author provided

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How green is our infrastructure? Helping cities assess its value for long-term liveability

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Silvia Tavares, Lecturer in Urban Design, James Cook University and Karine Dupré, Associate Professor in Architecture, Griffith University

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

How to grow crops on Mars if we are to live on the red planet

We can create the right kind of food plants to survive on Mars.
Shutterstock/SergeyDV

Briardo Llorente, Macquarie University

Preparations are already underway for missions that will land humans on Mars in a decade or so. But what would people eat if these missions eventually lead to the permanent colonisation of the red planet?

Once (if) humans do make it to Mars, a major challenge for any colony will be to generate a stable supply of food. The enormous costs of launching and resupplying resources from Earth will make that impractical.

Humans on Mars will need to move away from complete reliance on shipped cargo, and achieve a high level of self-sufficient and sustainable agriculture.

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Discovered: a huge liquid water lake beneath the southern pole of Mars

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The recent discovery of liquid water on Mars – which adds new information to the question of whether we will find life on the planet – does raise the possibility of using such supplies to help grow food.

But water is only one of many things we will need if we’re to grow enough food on Mars.

What sort of food?

Previous work has suggested the use of microbes as a source of food on Mars. The use of hydroponic greenhouses and controlled environmental systems, similar to one being tested onboard the International Space Station to grow crops, is another option.

This month, in the journal Genes, we provide a new perspective based on the use of advanced synthetic biology to improve the potential performance of plant life on Mars.

Synthetic biology is a fast-growing field. It combines principles from engineering, DNA science, and computer science (among many other disciplines) to impart new and improved functions to living organisms.

Not only can we read DNA, but we can also design biological systems, test them, and even engineer whole organisms. Yeast is just one example of an industrial workhorse microbe whose whole genome is currently being re-engineered by an international consortium.

The technology has progressed so far that precision genetic engineering and automation can now be merged into automated robotic facilities, known as biofoundries.

These biofoundries can test millions of DNA designs in parallel to find the organisms with the qualities that we are looking for.

Mars: Earth-like but not Earth

Although Mars is the most Earth-like of our neighbouring planets, Mars and Earth differ in many ways.

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The gravity on Mars is around a third of that on Earth. Mars receives about half of the sunlight we get on Earth, but much higher levels of harmful ultraviolet (UV) and cosmic rays. The surface temperature of Mars is about -60℃ and it has a thin atmosphere primarily made of carbon dioxide.

Unlike Earth’s soil, which is humid and rich in nutrients and microorganisms that support plant growth, Mars is covered with regolith. This is an arid material that contains perchlorate chemicals that are toxic to humans.

Also – despite the latest sub-surface lake find – water on Mars mostly exists in the form of ice, and the low atmospheric pressure of the planet makes liquid water boil at around 5℃.

Plants on Earth have evolved for hundreds of millions of years and are adapted to terrestrial conditions, but they will not grow well on Mars.

This means that substantial resources that would be scarce and priceless for humans on Mars, like liquid water and energy, would need to be allocated to achieve efficient farming by artificially creating optimal plant growth conditions.

Adapting plants to Mars

A more rational alternative is to use synthetic biology to develop crops specifically for Mars. This formidable challenge can be tackled and fast-tracked by building a plant-focused Mars biofoundry.

Such an automated facility would be capable of expediting the engineering of biological designs and testing of their performance under simulated Martian conditions.

With adequate funding and active international collaboration, such an advanced facility could improve many of the traits required for making crops thrive on Mars within a decade.

This includes improving photosynthesis and photoprotection (to help protect plants from sunlight and UV rays), as well as drought and cold tolerance in plants, and engineering high-yield functional crops. We also need to modify microbes to detoxify and improve the Martian soil quality.

These are all challenges that are within the capability of modern synthetic biology.

Benefits for Earth

Developing the next generation of crops required for sustaining humans on Mars would also have great benefits for people on Earth.

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Read more:
Before we colonise Mars, let’s look to our problems on Earth

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The growing global population is increasing the demand for food. To meet this demand we must increase agricultural productivity, but we have to do so without negatively impacting our environment.

The best way to achieve these goals would be to improve the crops that are already widely used. Setting up facilities such as the proposed Mars Biofoundry would bring immense benefit to the turnaround time of plant research with implications for food security and environmental protection.

So ultimately, the main beneficiary of efforts to develop crops for Mars would be Earth.

Briardo Llorente, CSIRO Synthetic Biology Future Science Fellow, Macquarie University

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

Tropical thunderstorms are set to grow stronger as the world warms

A supercell thunderstorm in the US state of Oklahoma.
Hamish Ramsay, Author provided

Martin Singh, Monash University

Thunderstorms are set to become more intense throughout the tropics and subtropics this century as a result of climate change, according to new research.

Thunderstorms are among nature’s most spectacular phenomena, producing lightning, heavy rainfall, and sometimes awe-inspiring cloud formations. But they also have a range of important impacts on humans and ecosystems.

For instance, lightning produced by thunderstorms is an important trigger for bushfires globally, while the hailstorm that hit Sydney in April 1999 remains Australia’s costliest ever natural disaster.

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Read more: To understand how storms batter Australia, we need a fresh deluge of data

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Given the damage caused by thunderstorms in Australia and around the world, it is important to ask whether they will grow in frequency and intensity as the planet warms.

Our main tools for answering such questions are global climate models – mathematical descriptions of the Earth system that attempt to account for the important physical processes governing the climate. But global climate models are not fine-scaled enough to simulate individual thunderstorms, which are typically only a few kilometres across.

But the models can tell us about the ingredients that increase or decrease the power of thunderstorms.

Brewing up a storm

Thunderstorms represent the dramatic release of energy stored in the atmosphere. One measure of this stored energy is called “convective available potential energy”, or CAPE. The higher the CAPE, the more energy is available to power updrafts in clouds. Fast updrafts move ice particles in the cold, upper regions of a thunderstorm rapidly upward and downward through the storm. This helps to separate negatively and positively charged particles in the cloud and eventually leads to lightning strikes.

To create thunderstorms that cause damaging wind or hail, often referred to as severe thunderstorms, a second factor is also required. This is called “vertical wind shear”, and it is a measure of the changes in wind speed and direction as you rise through the atmosphere. Vertical wind shear helps to organise thunderstorms so that their updrafts and downdrafts become physically separated. This prevents the downdraft from cutting off the energy source of the thunderstorm, allowing the storm to persist for longer.

By estimating the effect of climate change on these environmental properties, we can estimate the likely effects of climate change on severe thunderstorms.

Stormy forecast

My research, carried out with US colleagues and published today in Proceedings of the National Academy of Sciences, does just that. We examined changes in the energy available to thunderstorms across the tropics and subtropics in 12 global climate models under a “business as usual” scenario for greenhouse gas emissions.

In every model, days with high values of CAPE grew more frequent, and CAPE values rose in response to global warming. This was the case for almost every region of the tropics and subtropics.

These simulations predict that this century will bring a marked increase in the frequency of conditions that favour severe thunderstorms, unless greenhouse emissions can be significantly reduced.

Change in frequency (in days per year) of favourable conditions for severe thunderstorms for 2081-2100, compared with 1981-2000 averaged across 12 climate models under the RCP8.5 greenhouse-gas concentration scenario. Stippling indicates regions where 11 of the 12 models agree on the sign of the change.
CREDIT, Author provided

Previous studies have made similar predictions for severe thunderstorms in eastern Australia and the United States. But ours is the first to study the tropics and subtropics as a whole, a region that is characterised by some of the most powerful thunderstorms on Earth.

What drives the increased energy?

Different climate models, constructed by different research groups around the world, all agree that global warming will increase the energy available to thunderstorms – a prediction underlined by our new research. But we need to understand why this happens, so as to be sure that the effect is real and not a product of faulty model assumptions.

My colleagues and I previously proposed that high levels of CAPE can develop in the tropics as a result of the turbulent mixing that occurs when clouds draw in air from their surroundings. This mixing prevents the atmosphere from dissipating the available energy too quickly. Instead, the energy builds up for longer and is released in less frequent but more intense storms.

As the climate warms, the amount of water vapour required for cloud formation increases. This is the result of a well-known thermodynamic relationship called the Clausius-Clapeyron relation. In a warmer climate this means the difference in the humidity between the clouds and their surroundings becomes larger. As a result, the mixing mechanism becomes more efficient in building up the available energy. This, we argue, accounts for the increase in CAPE seen in our model simulations.

In our new study, we tested this idea in a global climate model by artificially increasing the strength of the mixing between clouds and their surroundings. As expected, this change produced a large increase in the energy available to thunderstorms in our model.

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Read more: Australia faces a stormier future thanks to climate change

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Another prediction of our hypothesis is that days with both high values of CAPE and heavy precipitation tend to occur when the atmosphere is least humid in its middle levels (at altitudes of a few kilometres). Using real data from weather balloons, we confirmed that this is the case across the tropics and subtropics.

What this means for future thunderstorms

The models predict that the energy available for thunderstorms will increase as the Earth warms. But how much more intense will storms actually become as a result?

The answer to that question is currently uncertain, and answering it is the next job for me, and other researchers around the world.

But it is clear that through our continued greenhouse gas emissions, we are increasing the fuel available to the strongest thunderstorms. Exactly how much stronger our future thunderstorms will ultimately become remains to be seen.

Martin Singh, Lecturer, School of Earth, Atmosphere and Environment, Monash University

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

Antarctica: Weed Invasion Threat

The article below reports on the threat to Antarctica posed by weeds brought in by human visitors. This is a threat that will continue to grow with climate change.

See also:
http://www.nytimes.com/2012/03/20/opinion/seeding-the-southern-continent.html