The Best Australian Science Writing 2014 (6 page)

If the forest were a financial system, trees would be its old money. Deeply rooted, they grow slowly, investing heavily over time in woody trunks and branches to support their leaves, and providing homes for a zoo of other species. Vines, on the other hand, would be the flashy junk-bond traders. Representing up to half of the plant species in a typical rainforest and producing up to 40 per cent of all leaves, they are down-and-dirty competitors. They invest almost nothing in supportive tissue, instead taking advantage of the trees' investments to scramble up to the top of
the forest and produce great flushes of leaves that bask brazenly in the full sun.

Francis Putz, a biologist at the University of Florida in Gainesville, highlighted this fraught relationship in a 1980 paper entitled ‘Lianas vs trees'. Lianas, or woody vines, can grow to be hundreds of metres long, with stems over half a metre across. Trees pay a high price for their presence. Lianas can strangle and deform a tree's branches, their dense foliage robs trees of life-giving sunlight, and their roots scarf up vital nutrients and water. Trees bearing lianas usually grow more slowly, reproduce less and die sooner than those without. Once lianas reach the canopy, they often climb laterally, effectively roping trees together so that, when one falls, it can drag down others. This is why loggers hate them: if they don't cut every liana linked to a tree before felling it, another may be yanked down on top of them. ‘Loggers call them “widow-makers”,' says Putz.

There are obvious reasons why some vines are becoming more prevalent. Humans have introduced invasive species, such as the rubber vine to northern Australia and kudzu to the southeastern US, that smother native forests, grasslands and waterways. Most vines are light-loving and increase rapidly in forests that have been fragmented by agriculture or selectively logged. Small, regenerating trees on the edge of disturbed forests provide ideal trellises for climbing quickly into the canopy. A decade ago, my colleagues and I revealed much higher liana abundances in fragmented than in intact Amazonian forests. Trees in these areas are beleaguered, dying two to three times as fast as normal.

* * * * *

But vines are also proliferating in undisturbed forests. Oliver Phillips of the University of Leeds in the UK and his colleagues revealed in 2002 that lianas had increased sharply at the expense
of trees at sites across western Amazonia. Something similar has been seen in nearly a dozen other intact forests in Central and South America. ‘It was controversial at first,' says Phillips, ‘but few doubt it now.'

What's happening? A likely cause is that tropical forests around the globe are becoming more dynamic, with trees dying and regenerating more rapidly – conditions that strongly favour vines. It is possible that global warming is intensifying windstorms that increase tree fall in the affected areas, yet there is little evidence for such an effect.

Instead, a more subtle driver seems to be at play: rapidly rising levels of atmospheric carbon dioxide. CO
₂
fuels photosynthesis, and the more there is, the faster plants grow. Faster growth creates more competition among plants for light, space and nutrients, which in turn drives higher rates of tree death and regeneration. Rising CO
₂
could also favour vines directly. Several studies over the past few years suggest that vines, with high photosynthetic rates, an abundance of energy-producing leaves and little costly supportive tissue, are primed to take advantage of rising CO
₂
.

This isn't to imply we know everything about the onslaught of vines. So far the trend has been spotted in undisturbed forests only in the Americas. Long-term studies are needed elsewhere to ensure this isn't a coincidence of geography. I wonder, too, about the fate of remote forests I have studied in the Congo basin. Vines there are naturally abundant because of disturbance by forest elephants. Yet elephant populations are collapsing from overhunting. Might vine numbers in these forests actually begin to decline?

Most evidence, however, suggests Earth is heading for a viney future. This worries ecologists like Stefan Schnitzer at the University of Wisconsin-Milwaukee. ‘Vines can change forests in a lot of ways,' he says. ‘They hit big, slow-growing trees far harder
than smaller, faster-growing species, meaning they can probably change the entire composition of the forest.'

It's not just trees that are at risk. Ainhoa Magrach, a postdoctoral colleague of mine at James Cook University in Cairns, has found that plants that live on trees, such as ferns, tend to be excluded in regions where vines are dense. These ferns are little islands of biodiversity, sustaining many animals in the rainforest canopy. A few species have mutualisms with aggressive ants that attack encroaching vines, but most are not so lucky.

The biggest worry is that proliferating vines could reduce carbon storage. Forests lock up billions of tonnes of carbon in woody tissue, and when vines kill or suppress trees some of that carbon is released into the atmosphere. Studies in Panama and Amazonia suggest rampaging vines capture just a small fraction of the carbon they cause trees to release. That could induce a positive feedback, with still more greenhouse gases and a warmer future for us all. If that goes too far, we really could be heading for a planet of the vines.

Antarctic ice: Going, going …

They're taking over!

Is there room for organics?

James Mitchell Crow

Western Australia at harvest time is a place of smoke and fire. By day, the signs are subtle: you need to come back in the relative cool of the night to witness the flames. Some fires burn in long orange-red stripes across the vast dark fields. Others are towering pyres. Death is in the air, but nobody is mourning. The fires are killing the seeds of multi-herbicide-resistant weeds, carefully collected during harvesting. Next year's weeds, nipped in the bud.

The WA weed fires are a recently established ritual. Twenty years ago, the farmers simply sprayed weedkiller to keep their fields weed-free, often diluting the chemical to save a few dollars. The weeds soon became immune to these chemical treatments, forcing the farmers to find new ways to control them.

Seed burning is one form of non-chemical ‘harvest weed seed control', a grassroots movement pioneered by farmers. If anyone could be said to lead this movement, though, it's Stephen Powles. Softly spoken, yet forthright and direct, there's a pragmatic air to Powles that speaks to his deep farming roots. Powles grew up on a New South Wales dairy farm. Today, he is an academic expert in weeds, researching them for 30 years. Powles directs the Australian Herbicide Resistance Initiative (AHRI) at the University of Western Australia.

‘Until recently, Australia had the world's biggest problems with herbicide-resistant weeds,' he says. That Australia no longer tops this list is a credit to Powles and his team's work alongside farmers. The 1990s were the most alarming time. During that decade, weeds resistant to farmers' two main classes of chemical herbicides spread quickly across the grain belt, threatening yields. To protect their crops, Australian farmers started hunting for non-chemical means to keep the weeds down, helped by AHRI researchers. Intercepting and destroying the weeds while they are still seeds, burning or mechanically crushing them, is proving particularly effective.

The success of these chemical-free weed treatments could be considered a nod toward organic farming, although Powles is at pains to point out that these ‘organic' approaches were developed on conventional farms, and they are still combined with careful applications of herbicides that do still work, such as glyphosate and paraquat. Australian wheat farmers are simply using every trick and tool they can come up with to keep food production high.

But are all of these tools – in particular, the synthetic herbicides, fertilisers and pesticides the farmers use – really necessary? Avoiding any use of synthetic herbicides, pesticides and fertilisers is the fundamental tenet of organic food production. Could this approach ever offer a sustainable, secure way to feed the world's rapidly growing population?

* * * * *

It's hard to pinpoint the exact moment when the organic farming movement began. The first shoots seemed to spring up in the 1940s and early 1950s in multiple places from the US to Europe. In the UK, the Soil Association was established in 1946 over concerns that intensive, industrialised agriculture was damaging
soil, the environment and the nutritional value of food. In 1967, its first organic standards were drawn up. More recently, these groups have campaigned vociferously against genetically modified crops.

The Soil Association is one of many organic advocacy groups to claim that GM crops aren't needed to feed our growing global population. In fact, never mind GM, it says we don't even need synthetic fertilisers, pesticides or herbicides. All it takes is organic farming, according to their recent position statement
Feeding the Future: How organic farming can help feed the world
. It's an optimistic view given that certified organic agriculture is currently a niche activity accounting for less than 1 per cent of the world's farmland. In some areas, most farming is by necessity organic. These include Africa, where people are simply too poor to afford chemicals, and Cuba. Havana has become a poster-child for organic supply – with any available land reclaimed for organic food crops – but the story of organics in the countryside is one born of necessity. In the early 1990s, Cuba's supply of Soviet fuel, fertilisers and pesticides was abruptly cut off. But the idea the island feeds itself purely by organic means is a myth – best guesses suggest that between 40–50 per cent of Cuba's food is imported.

* * * * *

It is early evening when I call organic farmer Raoul Adamchack at his California home to ask his views on this question. One of his children answers the phone – ‘Dad, there's some English journalist on the phone for you' – and we talk over the comforting background clatter and hum of a family preparing dinner.

Adamchak is a committed organic farmer. ‘I started in the mid-70s, which was a very environmentally conscious time,' he recalls. Agent Orange was still fresh in the memory, and the battle to ban the environmentally damaging pesticide DDT was
still raging. ‘The idea, for me, of applying pesticides that would affect my health, or the health of beneficial insects, or the health of my customers, seemed so alien that organic farming seemed like the way to go. And I've been doing it more or less ever since.'

Today, Adamchak runs the organic market garden at the University of California Davis, teaching students organic vegetable production. He speaks passionately and candidly about the challenges of organic farming. ‘It's not easy,' he says. ‘You lose some of your crop to pests that you just aren't able to deal with.'

He comes across as a very pleasant man, and having been invited via phone line into his home, I find myself reluctant to challenge him on the standard organic doctrine that we should forget GM and let organic feed the world.

Talking to Powles in an earlier phone call, I'd had no such worries. I hadn't got the feeling he was a man who would argue strongly for organic farming, despite his battles with weed killer resistance. Powles had dispatched the question with typical efficiency: ‘The serious analyses say that if we were to have widespread organic farming, we would have a 30 per cent reduction in food production.' In 2012, for example, an analysis in the journal
Nature
compared 66 recent studies and reported that organic crop yields were, on average, 25 per cent less than at conventional farms. To maintain current levels of food production on an organic-only planet we'd have to expand farmland at the cost of natural habitat – hardly an ecologically sound solution.

Bracing myself, I ask for Adamchak's view. His answer is a surprise, although given his frank and honest answers to earlier questions, perhaps it shouldn't be. ‘The challenge for organic agriculture is to help solve the global issues of feeding people in the face of climate change and with increasing population,' he says. ‘On some level, it becomes clear that organic agriculture isn't going to be able to do that by itself. No matter how you figure it, there aren't enough animals making enough waste to
fertilise more than a small fraction of the cropland that we need.'

This fertiliser problem – that the world's natural sources of nitrogen are no longer enough to keep the world's growing population fed – first became apparent in the closing years of the 19th century. Thanks to German chemist Fritz Haber and industrial engineer Carl Bosch, we can now ‘fix' nitrogen from the air to make synthetic fertiliser, albeit in an energy-intensive process. At the time their process swung into production in 1913, the global population stood at 1.6 billion. Agronomists like Vaclav Smil from the University of Manitoba estimate that if we were to rely on organic sources, agriculture could feed only four of the seven billion people now sharing the planet.