Canny breeding creates vitamin A-rich maize without genetic modification

On Thursday, I wrote about a way of genetically modifying carrots to turn them into rich sources of calcium. The method could be more widely used in vegetables to help reduce nutritional deficiencies, but it risks raising the ire of the anti-GM environmentalist camp. But there is another way of altering the genes of crop plants that avoids such controversy, and it’s a traditional one – selective breeding.

By cross-breeding individuals with desirable qualities, farmers have been tinkering with the genes of both animals and plants for centuries. Traditionally, the process has been a bit messy. Genes don’t always easily translate into physical characteristics, so there is a certain amount of trial-and-error involved.

Now, Carlos Harjes from Cornell University had developed a way of using modern genetic techniques to make selective breeding even more selective. For his first trick, he has developed a variety of maize to combat vitamin A deficiencies. Best of all, no genes were added, tweaked or subtracted in the making of this vegetable – he only used the natural genetic variation within the world’s maize strains.

Loss of big mammals breaks alliance between ants and trees

The natural world is full of alliances forged between different species, cooperating for mutual rewards. The relationship between ants and acacia trees was one of the first of these to be thoroughly studied. But new research suggests that this lasting partnership may be sundered by the unlikeliest of reasons – the decline of Africa’s large mammals.

Acacias are under constant attack from hungry animals, from tiny caterpillars to towering giraffes. In response, many species like the whistling-thorn tree (Acacia drepanolobium) recruit colonies of ants as bodyguards. Any hungry herbivores eager to chomp on the acacia’s leaves quickly get a mouthful of biting, stinging ants. The tree is a fair employer. In return for their services, its ant staff receive a sugary and nutritious nectar as food and hollow swollen thorns called ‘domatia’ as board.

But this pact is a fragile one. Todd Palmer from the University of Florida and colleagues from the USA, Canada and Kenya have found that it rapidly breaks down if the large animals that graze on the acacia disappear. Without the threat of chomping mouths, the trees reduce their investments in bodyguards to the detriment of both partners.

Palmer demonstrated this with plots of land in Kenya’s Laikipia Plateau, where fences have kept out large plant-eaters for over a decade. Since 1995, no herbivore larger than a small antelope has entered the four-hectare “exclosures” in an attempt to study the effect of these animals on the local ecology.

Within these 10 years, Palmer found that the majority of trees produced fewer domatia and less nectar and unexpectedly, the strongest alliances were hit the hardest. What were once happy partners quickly became selfish rivals.

Ancient plants manipulate insects for hot, smelly sex

For plants too, sex can be a hot and smelly affair. In most plant-insect partnerships, the pollinator seems to do most of the work by voluntarily transferring pollen from plant to plant in exchange for a meal.

But an ancient lineage of plants – the cycads – takes more active steps to ensure its future with a bizarre combination of heat and smells. In the afternoon, they use heat and a toxic stench to drive insects out of male cones only to lure them into female cones in the evening with a more alluring scent.

New plant species arise from conflicts between immune system genes

Plants from the same species can fail to breed together because incompatible genes from the parents cause the offspring’s immune system to fatally turn on itself. These conflicts between otherwise normal genes could split groups of the same plant into separate species.

“Congratulations, it’s a stunted, malformed, necrotic hybrid!” Those aren’t really the words that new parents want to hear but thankfully, plants aren’t in a position to be that upset.

In several species of plants, a surprising number of offspring turn out to be malformed hybrids that quickly wither and die. Now, Kirsten Bomblies and colleagues from the Max Planck Institute for Developmental Biology have found out why.

Two genes, one passed down by each parent, ignite an reaction in the hybrid youngster that turns its immune system against it. It’s not a genetic disorder; neither gene was faulty and both were harmless in their native parental environments. But they evolved apart from each other and make poor bedfellows when united.

They behave like employees from two merging companies. Having developed in different backgrounds and working cultures, they can find it difficult to work together, lowering the productivity of the new business.

Over time, these incompatibilities could drive wedges between different plant strains, reducing their chances of successful mating and turning separate strains into separate species.

Human nitrogen emissions indirectly capture carbon by fertilising forests

Human activity has greatly increased the levels of active nitrogen in the environment. By acting as a fertiliser and speeding the growth of forests, this extra nitrogen has indirectly locked up more carbon dioxide in the world’s trees.

There is no doubt that of all the elements in the entire periodic table, carbon is currently hogging the limelight. As it cycles through our environment, the policy decisions and economic futures of entire countries hang in the balance.

For all its media-whoring, you might be forgiven for forgetting that carbon is not the only element we are belching into the environment. Over the last century, we have greatly overwhelmed the natural nitrogen cycle too.

Nitrogen – the neglected element

Through the manufacture of nitrogen-based fertilisers and the exhausts of our cars, power plants and factories, we have more than doubled the natural levels of active nitrogen in the atmosphere.

Nitrogen is a valuable commodity in many parts of the world, and restricts the growth of local plant life. As such, the recent man-made influx has led to large increases in plant growth. In some cases like algal blooms that choke rivers and lakes, it’s too much of a good thing. But there is a silver lining.

Federico Magnani from the University of Bologna, together with an international team of scientists, have found that the changes in the nitrogen cycle may have been inadvertently fertilising our forests.

Carbon and nitrogen

The world’s forests act as massive carbon sinks, delaying the global warming effects of carbon dioxide by trapping it in prisons of wood and leaves. And larger forests mean more trapped carbon. The temperate forests of the Northern Hemisphere alone could store a massive 600 megatonnes of carbon every year.

The carbon and nitrogen cycles dance around each other in complex ways. When nitrogen levels increase, forests respond by channelling growth from roots to leaves and trunks. These above-ground organs are more enduring than roots and retain sequestered carbon for a longer time. More leaves also means increased photosynthesis, which serves to draw more carbon dioxide in from the air.

The extra nitrogen also delays the decay of leaf litter, further halting the release of organic carbon into the atmosphere.

Magnani’s colleagues are not the first group to try and look at the interplay between nitrogen levels and carbon capture. But other studies have found it difficult or impossible to account for the effects of nitrogen alone.

Carbon balance

A forest’s carbon balance – the amount of carbon trapped versus the amount released – depends on a variety of factors, including its age, logging, fires, and more. Some of these are easy to account for at a small scale. For example, when logging or fires kill off patches of forest, they become net sources of carbon as they start to regrow.

But after a couple of decades or so, the mature forest turns into a carbon sink, and the amount it stores outweighs the amount it releases. Clearly, a forest’s carbon balance changes as it matures, but real forests consist of patches of vegetation are very different ages.

To look at the overall picture, Magnani’s group took direct measurements of the carbon balance over a long period of time, from a network of forest sites in Western Europe and the USA. This allowed them to account for short-term sources of variation. And by using direct measurements, they have surpassed the models and simulations of previous studies.

The group found that carbon balance corresponds well with nitrogen levels in the area. In fact, the prowess of some forests at carbon capture seem to be overwhelmingly driven by their extra nitrogen boost. Our effects on the nitrogen cycle may have been acting like an unexpected carbon offset scheme.

Practicalities

So should we start pumping nitrogen in our forests to trap more carbon dioxide? Certainly, Magnani’s results suggest that small extra amounts of nitrogen can cause unexpectedly large levels of carbon capture. But his view and those of other commentators is a resounding “Not yet”.

There are still many questions left to be answered, particularly about the exact relationship between nitrogen addition and carbon levels. There is some evidence that some temperate forests are suffering from nitrogen saturation. Could adding more nitrogen damage them, or prevent them from returning to a situation where nitrogen is limited and not free-flowing?

And what of the other risks and benefits? The extra wood from the faster-growing trees could find a use as a replacement for concrete, a notoriously eco-unfriendly building material. But additional nitrogen could affect other animals and plants in the local environment. Would biodiversity suffer if certain species monopolise the newfound nitrogen bonuses?

As future research addresses these questions, those involved in forest management would do well to heed the importance of the world’s forests in sequestering carbon dioxide. There are other ways of increasing forest coverage besides mass-fertilisation, and the most obvious one is safeguarding the forests that we already have!

Reference: Magnani, Mencuccini, Borghetti, Berbigier, Berninger, Delzon, Grelle, Hari, Jarvis, Kolari, Kowalski, Lankreijer, Law, Lindroth, Loustau, Manca, Moncrieff, Rayment, Tedeschi, Valentini & Grace. 2007. The human footprint in the carbon cycle of temperate and boreal forests. Nature 447: 848-850.

Technorati Tags: carbon cycle, nitrogen cycle, nitrogen emissions, forests, carbon sequestration, science

Of flowers and pollinators – a case study in punctuated evolution

Darwin predicted that flowers and pollinators are engaged in an evolutionary arms race. But that’s not always the case. In a group called columbines, evolution happened in a stop-start ‘punctuated’ way, as the flowers encountered new pollinators with increasingly long tongues.

Charles Darwin was a visionary in more ways than one. In 1862, Darwin was studying a Malagasy orchid called Angraecum sesquipedale, whose nectar stores lie inaccessibly at the bottom of a 30cm long spur (tube). Darwin predicted that the flower was pollinated by a moth with tongue long enough to raid the spur.

Few people believed him, but in 1903, zoologists discovered Darwin’s predicted moth, Xanthopan morgani praedicta, and it did indeed have a very long tongue. Darwin’s accurately predicted the extraordinary but matching lengths of moth tongue and orchid spur, but his explanation for them is another story.

The arms race model

He suggested that the two species were locked in an ‘evolutionary arms race’. Orchids and pollinators gradually co-evolved over time, lengthening both tongues and spurs in response to each other.

Orchids with the longest spurs have an advantage. Their nectar stores are only just within reach of pollinators, so they are tempting but don’t sacrifice too much valuable nectar. For pollinators, the advantage belongs to those with the longest tongues because they have access to the most food.

The arms race model has become widespread and popular since Darwin’s time. It helps to explain relationships between predators and prey, parasites and hosts and even males and females. But its original function – to explain the relationship between flowers and pollinators – has just been called into question.

Columbines

Justen Whittall and Scott Hodges from the University of California, Santa Barbara, tested the arms race theory by looking at another long-spurred flowering plants – the columbines (Aquilegia sp). In these flowers, every petal carries its own elongated nectar spur and the advent of these spurs coincided with the recent and rapid diversification of this group.

Whittall and Hodges charted the evolutionary relationships between the 25 North American columbine species, whose spurs range form barely a centimetre in length, to just over twelve. They found that this great variety of lengths was driven by changes in pollinators, rather than gradual races against a single one.

The flowers with the shortest spurs were pollinated by short-tongued bumblebees. Hummingbirds, whose tongues are longer, pollinate columbines with longer spurs, while hawk-moths, with the longest tongues of all, carry the pollen of the longest-spurred flowers.

There is no overlap between these three groups and once a lineage switches pollinator it doesn’t go back. Over the course of their evolution, the columbine lineages went from bumblebees to hummingbirds, and then to hawkmoths, lengthening their spurs with every jump.

The ‘pollinator shift’ model

Based on these observations, Whittall and Hodges put forward an alternative to Darwin’s arms race model. They imagined a columbine ancestor that was well adapted to the tongue length of a specific pollinator (say, a bumblebee).

In part of its range, the flower started to be visited by a second pollinator (say, a hummingbird) with a much longer tongue. In this area, the plant rapidly evolved a longer spur in response to its new partner and over time, this led to two species with different spur lengths and different pollinators.

In this model, the columbines’ spurs evolved in a ‘punctuated’ stop-start way, very different to Darwin’s model of gradual change. Each pollinator shift triggered a large evolutionary rush, as the species lengthened their spurs in response to the longer tongues of their new partners. In between these shifts, the pace of evolution slowed down considerably.

But Darwin’s arms race idea isn’t out for the count yet. Whittall points out that columbines that are pollinated by hawkmoths have a great variety of spur lengths themselves that were most likely the result of an arms race. And the moths themselves evolved long before the columbines did, so the variations in their tongue lengths must have evolved in relationships with other plants.

An adaptive valley

The stop-start model also explains a difference between columbines around the world. Those in Europe and Asia have a much smaller range of spur lengths than their North American cousins, and none of them are pollinated by hawkmoths. Whittall and Hodges have an answer for this too – it’s because Eurasia has no hummingbirds.

Imagine if flowers tried to make the evolutionary leap from bumblebee to hawkmoth without the intermediate stepping stone of hummingbirds. At the intermediate spur length, the flower would have excluded its old pollinator, whose tongues would now be too short to reach any nectar. But it would have no advantage over its new pollinator, whose amply long tongues could drink the flowers dry.

Between bumblebee and hawkmoth lies an ‘adaptive valley’, where intermediate-length flowers have no advantage and are ignored by natural selection. In Eurasia, there is not enough impetus for a species to cross it. But North America, the hummingbirds act as a stepping stone that allowed the columbines to ford this gap and evolve even more extreme flowers.

Reference: Whittall & Hodges. 2007. Pollinator shifts drive increasingly long nectar spurs in columbine flowers. Nature 447: 706-709.

Technorati Tags: Justen Whittell, Scott Hodges, orchids, columbines, nectar spurs, flower evolution, evolutionary arms races, punctuatedevolution, hawkmoths, pollinators, science

Images: Moth from MSN Encarta, columbine montage from Justen Whittall’s website.

Related stories about evolution:
Natural selection does a handbrake turn – quick evolution at work
Salamander robot walks, swims and sheds light on evolutionary step from sea to land
Human cone cell lets mice see in new colours
Living optic fibres bypass the retina’s back-to-front structure
Viruses evolve to be more infectious in a well-connected population
The evolution of animal personalities – they’re a fact of life

The effect of GM crops on local insect life

A large study weighs up the existing evidence on the impact of GM crops on local insect life, providing some much-needed scientific rigour to the GM debate.

In Europe, the ‘GM debate‘ about the merits and dangers of genetically-modified (GM) crops is a particularly heated one. There is a sense of unease about the power of modern genetic technology, and a gut feeling that scientists are ‘playing God’. These discontents are stoked by the anti-GM camp, who describe GM crops with laden and fear-mongering bits of unspeak like ‘Frankenstein foods’ and ‘unnatural’.

In a debate so fuelled by emotion and personal values, scientific research and a critical analysis of the evidence rarely gets a look-in. But science has to grudgingly admit some blame in this, because there is actually precious little research on the safety of GM crops. And many of the studies that have been done were short-term and poorly replicated.

A lack of research is dangerous. It provides opening for people on either side of the debate to quote single, small studies as canon and brushing aside any research that contrasts with their stances.

Adding evidence to the debate

Michelle Marvier and colleagues from Santa Clara University, California, are trying to change all that. They have analysed over 42 field experiments on GM crops to get an overall picture about their safety. The technique they used is called meta-analysis, a statistical tool that asks “What does everyone think?” It works on the basis that individual small studies may be far from conclusive, but pooling their results together can lead to stronger and more accurate results.

They looked at three strains of GM-crops that had been modified with genes from a soil-dwelling bacterium called Bacillus thuringiensis. The transferred genes are responsible for producing a number of biological (and therefore ‘natural’) insecticides. When moving them across to plants, geneticists typically try to match the insecticide to the pest they are trying to fight. (In the image on the right, Bt-peanut leaves are protected from the damaging European corn borer)

The toxins are delivered at high dosages to pests, but are restricted to the plant (and sometimes even to particular tissues). They can also be added to the chloroplast genome, which is quite separate form the plant’s nuclear DNA. This stops them from being transferred to other plants.

The hope is that these so-called ‘Bt crops’ can help to minimise the collateral damage of less targeted insecticide sprays. In theory, only pest insects that eat valued crops are killed, while the rest of the ecosystem is unharmed.

The results

That’s what Marvier set out to test. She looked at field experiments which tested the impact of caterpillar-resistant cotton and maize plants on the abundance of other groups of insects and invertebrates.

She found that these other creatures are found in greater numbers in fields containing the caterpillar-resistant GM plants, compared to those sprayed with conventional insecticides. However, the GM crops also led to slightly lower numbers of non-targeted insects compared to fields where no GM crops and no insecticides were used.

The results stayed the same even when Marvier analysed them in more detail. For example, she found much the same thing when she only looked at experiments that had been published in peer-reviewed scientific journals.

So assuming that Bt crops do indeed reduce the use of insecticides (and that’s far from proven), then they will also, as claimed, reduce the collateral damage caused by these chemicals. But they’re not as good for the environment as using no insecticides at all, be they engineered or sprayed.

The bigger picture

At the local level, Marvier’s study provides some much-needed scientific backbone to the GM debate. But the real decisions need to be weighed up at a larger level. For example, it’s all well and good to say that a no-insecticide, no-GM field is the best solution, but that leaves farmers in a bit of a lurch.

One of the big criticism levelled against organic farming is that it leads to lower yield than other practices and requires more agricultural land to be viable and that deals a bad hand to farmers in the developing world. This in turn could lead to deforestation and habitat loss.

On the other hand, Marvier advises caution when interpreting her work. This study has revealed just one benefit of GM crops and even then, only for one specific type of genetic modification. Many of the studies involved isolated patches of land, rather than entire farming systems, where the situation is more subtle. Not all non-GM crops are sprayed with insecticides, while not all GM crops are free from them.

Any benefits must also be weighed against potential health or environmental risks, and again, these must be researched carefully.

To Marvier, the clearest message from her study is that we have started to accumulate enough data to look at this issue from an empirical, evidence-based point of view. If we are to make sound decisions, there is little room for anecdotal evidence or knee-jerk responses guided by personal philosophy.

Bt hypocrisy

For example, there is a certain irony to the opposition to Bt crops. Because its insecticides are ‘natural’, the bacterium is one of the few pesticides that organic farmers are allowed to spray onto their crops.

The bacteria of course use the exact same genes that are transplanted into Bt-engineered crops. Some may argue that this method is better because it is more ‘natural’, because the genes stay within the organism they were intended for. But is that really better?

Wholesale Bt spraying is a crude technique than the specific and targeted use of Bt-engineered crops. It means that the surrounding land is also covered in the bacteria and creatures other than pests are exposed to its entire gamut of toxins. And because farmers need constant supplies of the bacteria, it soaks up more money.

Reference: Marvier, McCreedy, Regetz & Kareiva. 2007. A meta-analysis of effects of Bt cotton and maize on nontarget invertebrates. Science 316: 1475-1477.

Technorati Tags: GM crops, genetic modification, GM safety, GM environment, GM debate, insecticides, Michelle Marvier, Peter Kareiva, Bt crops,

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Genetically-modified mosquitoes fight malaria by outcompeting normal ones
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Feed the world – turning cotton into a food crop

Carbon offset schemes worsen global warming if trees are planted in the wrong places

Many carbon offset schemes rely on planting new trees to counteract rising carbon dioxide levels and the climate change they cause. But new research shows that these schemes only work if trees are planted in the tropics. Plant elsewhere, and you’ll only be adding to global warming.

Plant a tree and save the planet. If it sounds too good to be true, it’s usually because it is.

It is now crystal clear that modern global warming is a man-made phenomenon. But with this acceptance comes guilt, and the quest to find ways of mitigating our energy-hungry lifestyles

On the surface, carbon offset schemes appear to offer a win-win solution. People can assuage their guilt over yet another business flight, or drive to the shops, by paying for trees to be planted or investing in renewable technology.

Trees act as carbon sinks, sucking the gas in from the air and shunting the carbon atoms across into the plants’ own molecules. So plant enough trees, and the emissions you are responsible for will effectively be negated. You can whistle a jaunty tune and slap a carbon-neutral sticker on your car.

That’s the theory anyway. But Govindasamy Bala and colleagues form the Lawrence Livermore National Laboratory have found that it’s not just what you plant that matters, it’s where.

They ran complex simulations of how the planet’s climate would change if trees in different parts of the world were removed or restored. Unexpectedly, they found that overall, deforestation cools the planet down, and adding new trees in some regions may actually fuel global warming.

In a simulation where all the world’s trees were removed, the global temperature fell by about 0.3 degrees Celsius.

Why should this be? After all, trees soak up carbon dioxide and store carbon in their bodies – this keeps the planet cool. They release water vapour into the air, which forms clouds that reflect solar radiation away form the earth, again resulting in cooling.

But forests are also dark and by absorbing the energy from sunlight, they heat the planet too. According to Bala’s simulation, this heating effect outweighs the cooling ones.

When Bala looked at the effect of deforestation in specific areas, a clearer picture emerged. The tropical rainforests are doing their bit in fighting global warming by forming clouds and absorbing carbon dioxide. Their loss led to a rise in global temperature.

In contrast, the temperate and polar forests aren’t pulling their weight. These verdant slackers heat the planet themselves by absorbing solar radiation. Without them, the underlying snow would reflect more of the sun’s energy into space and we’d get a cooler planet.

These experiments suggest that tree-planting will only help to restrain global warming as planned if it happens in the tropics. In other parts of the world, it could even do more harm than good. When it comes to carbon offset schemes, the devil’s in the details.

Bala and his co-workers are modest on their work and are quick to point out that it is based on a single simulation. And they are careful to quickly stem the inevitable backlash from anti-environmental groups, who may well perversely suggest that this data warrants declaring war on trees.

Forests clearly have value beyond their influence on temperature. They harbour a great richness of life, keep the soil together and stop the oceans from acidifying by storing carbon dioxide – the list goes on. Deforestation is clearly not a solution to global warming, but wanton re-forestation won’t do any good idea.

Bala’s study gives pause for thought to those of us who seek to placate our environmental consciences by paying into carbon offset schemes.

At the very least, the details of any schemes should be checked carefully. Even better, serious thought should be given to preventive measures, like reducing car or plane use, rather than cures.

 

Reference: Bala, Caldeira, Wickett, Phillips, Lobell, Delire & Mirin. 2007. Combined climate and carbon-cycle effects of large-scale deforestation. PNAS 104: 6550-6555.

Technorati Tags: carbon+offset, climate+change, global+warming, deforestation, trees, environment, science

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Opinion: How biofuels could cut carbon emissions, produce energy and restore dead land

A new way of producing biofuels could not only curb carbon emissions and produce renewable energy, but also restore unusable agricultural land and improve biodiversity. But only if this winning breakthrough find its way onto the political agenda.

The twenty-first century is having a troubled infancy. Six years in and it is facing the twin perils of climate change and a looming energy crisis. Solutions to both are in high demand and many research dollars and pounds are being channelled into developing environmentally-friendly, renewable resources.

Biofuels – the product of living things – certainly fit the bill, being both renewable and biodegradable. But there is always a catch. Currently, biofuels are a matter of harvesting single crops grown on fertile soils such as corn or sugarcane or waste products such as straw.

In George Bush’s State of the Union address of January 2007, corn-based biofuels played a major role in reducing the USA’s dependence on oil. But it is highly unlikely that these fuels will make a large dent in America’s energy demands.

The fuel-bearing plants need land to grow on, and the choice becomes either using up current agricultural land that provides much-needed food for growing populations, or to clear natural land and damage the ecosystems they nourish.

Any new crops must also be irrigated and treated with potentially polluting fertilisers and pesticides. And the water, chemicals and eventual crops must be transported with fossil-fuel-burning vehicles.

At first glance, biofuels seem to create more problems than they solve. In an ideal world, we would source biofuels from crops grown on used land with no other agricultural value, with a minimum of chemical help.

But such a world may be just round the corner, thanks to scientists from the University of Minnesota. David Tilman, Jason Hill and Clarence Lehman have discovered that the key to low maintenance biofuels is diversity.

The trio cultivated plants in 152 plots on agriculturally degraded soil (see left; photo taken by David Tilman), with low levels of the nitrogen that crop plants need to thrive on. They were irrigated once when the crops were planted, and left untouched by fertilisers.

They found that plots which cultivated a variety of plants produced far more energy than those with a single species, with the most productive ones containing 16 different species.

These so-called ‘low-input, high-diversity’ or LIHD plots contained a mix of humble woody plants, legumes and grasses, such as wild lupine, goldenrod, and switchgrass.. They produced over three times as much energy as monocultures of single species.

Tilman found that every hectare of the LIHD plots yielded 68 gigajoules of energy a year but because they were so low maintenance, they only needed 4 gigajoules to pay off the energy debt of production, harvesting and transport. At processing plants, the fuels can be converted into gasoline, diesel and electricity.

In this way, each hectare of LIHD plots produce over 50% more usable energy on abandoned soil than other crops do with fertile soils.

Part of the LIHD crops’ success lay in the fact that legumes can seed impoverished soils with valuable nitrogen. Over the decade the experiment ran for, nitrogen levels in the LIHD plots increased by a quarter.

The biological diversity in each plot also warded against diseases and marauding species, never allowing a single invader to gain a proper foothold. This greatly reduced the need for pesticides and chemical protections.

Providing an alternative to fossil fuels is just one way in which LIHD biofuels could help to curb carbon emissions – they also act as carbon sinks. Monocultured crops such as corn and soybean produce less greenhouse gases than petroleum-based petrol and diesel, but they are still carbon-positive – their production leads to a net increase in carbon dioxide.

In contast, LIHD biofuels are carbon-negative, removing carbon dioxide from the atmosphere and storing it in both the soil and the growing roots of the plants themselves.

This stored CO₂ outweighs the total amount emitted during production and transportation by more than ten times and every hectare of crop captures about 4 tonnes of carbon dioxide every year. Compared to corn-based biofuels, the greenhouse gas reductions achieved by LIHD fuels were 6-16 times greater.

The world currently has at least 500 million hectares of agriculturally abandoned land that serves no fruitful purpose, and could be used to sow LIHD crops. The resulting biofuel harvest could replace 13% of the world’s petroleum consumption and 19% of its electricity needs.

LIHD biofuels are an environmentalist’s dream, and could provide a very rare win-win situation for the world’s energy providers. They represent a way of providing renewable energy while reducing carbon emissions, conserving biodiversity and both using and renewing otherwise degraded land.

It is an opportunity that scientists need to explore further and the world’s policy-makers need to start taking seriously.

 

Reference: Tilman, Hill & Lehman. 2006. Science 314: 1598-1600

Technorati Tags: Biofuels, LIHD, carbon emissions, renewable resources, science

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Human nitrogen emissions indirectly capture carbon by fertilising forests
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Feed the world – turning cotton into a food crop

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Feed the world – turning cotton into a food crop

The world’s cottonseed harvest have enough protein to feed half a billion people in the world’s poorest places, but are inedible because they contain a potent poison. Now, scientists have found a way of removing that poison, and turning cotton into a stunning new food source.

 

“Feed the world. Let them know it’s Christmas time.” The world is currently home to 6.5 billion people and over the next 50 years, this number is set to grow by 50%. With this massive planetary overcrowding, Band Aid’s plea to feed the world seems increasingly unlikely.

Current food crops seem unequal to the task, but scientists at Texas University may have developed a solution, a secret ace up our sleeves – cotton.

Cotton is famed for its use in clothes-making and has been grown for this purpose for over seven millennia. We do not think of it as a potential source of food, and for good reason.

The seeds of the cotton plant are rife with a potent poison called gossypol (see below) that attacks both the heart and liver. Only the multi-chambered stomachs of cattle and other hooved animals can cope with this poison, relegating cottonseed to a role as animal feed.

Getting rid of gossypol could go a long way to reducing the world’s hunger crisis. A fifth of a cottonseed’s weight is made up of oil, and a quarter of high-quality protein. For every kilogram of fibre, each cotton plant produces 1.65 kg of seed.

And the plant is grown in over 80 countries by some 20 million farmers, the majority of whom live in the poorest parts of the world, where starvation is an ever-looming threat. If only the seeds could be made edible.

In 1954, scientists attempted to launched a programme to cross-breed normal cotton plants with a mutant strain that lacked the glands that make gossypol. Unfortunately, they discovered that cotton creates the poison for a reason.

It infuses the plant’s various tissues, protecting it from insect pests and infections alike. The programme’s seeds were safe for human consumption, but the weakened plants readily succumbed to insect attacks, destroying their commercial potential.

Now, Ganesan Sunilkumar and colleagues have solved the problem. They have used a technique called RNA interference, or RNAi, to turn off a gene called delta-cadinene synthase, which is essential for gossypol production.

But in this case, the team put their system under the control of a genetic switch used only in cotton seeds, and not the rest of the plant. As a result, levels of gossypol plummeted in the plant’s seeds and these alone. The rest remained as strong as ever against attackers.

Sunilkumar ran their special plants through a series of tests to make sure that the RNAi’s effects never spread to the rest of the plant. They passed every one. Best of all, the altered plants stably passed on their characteristics to their daughters.

This study is testament to both the power and the precision of modern genetic technology. The researchers identified a very specific point in a biochemical pathway and blocked it in a single part of the plant. The result is a variant that retains the original’s survival abilities, but is suddenly fit for human consumption.

Their approach has tremendous potential for opening up other food sources. For example, the beans of the tropical grass pea, Lathyrus sativus, are often eating by poor people in Africa and Asia in times of dire need.

As the beans contain a potent neurotoxin – a nerve poison – those eating them often contract a neurological disease called lathyrism. With Sunilkumar’s technique, lathyrism could become a thing of the past.

For those who feel that the use of such technology is tantamount to playing God, consider this. Every year, 44 million tons of cottonseed are wasted. With this new technology, the engineered seed could provide enough protein for half a billion people every year.

Sunilkumar, Campbell, Puckhaber, Stipanovic & Rathore. 2006. PNAS 103: 18054-18059.

Technorati Tags: cotton, gossypol, food shortages, famine, world hunger, genetic engineering, GM crops, RNAi, science

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