Sticky times for the maple tree

As April Fool's Days jokes go, the one about exploding sugar maple trees was pretty good. Apparently, the low-carb diet (all the rage a few years ago) had led to a steep fall in demand for maple syrup, the National Public Radio announcer solemnly intoned. As a result maple trees were being left untapped, turning them into time bombs of pent-up sap that could go off at any time - and did.

Needless to say, when that same announcer reported that the health authorities in Vermont - the state most celebrated for production of this uniquely North American delicacy - had already reported 87 deaths and 140 maimings of people who had strayed too close, you suddenly remembered that the date was 1 April 2005 - even if you did vaguely continue to wonder what might happen to maple trees when there could be no escape for surplus sap.

That same day an NPR listener, entering into the spirit of things, came up with a fine solution: why not train local squirrels to colonise the neglected maples during winter? That way they could nibble the bark to allow the trees to let off steam (or rather, sap) before anyone might get hurt by flying timber.

There is, however, a touch of irony at this point. Red squirrels native to the region actually do rip open the bark of maples when their other food sources are blanketed in snow. The sap flows out, and evaporates in the winter sun. The squirrels then return to gobble up crystallised sugar. One way and then another, the line between fiction and fact in the lore of the sugar maple can be blurred.

But now a real and far more serious threat is afoot, and this time not to unwary humans, but to the trees themselves. Climate change is pushing the North American maple zone gradually but inexorably northwards towards Canada.

One day it may be gone. Without the maple, Vermont would not be Vermont. Mention the name of this beautiful, quirky and fiercely Democratic sliver of New England wedged against the Canadian border, and maple is probably the first association that comes to mind.

The tree itself comes to mind, which in autumn produces the dazzling palette of colours that lures tourists from all over the world - but also the famous and delicious aromatic syrup that is derived from its sap.

In plain economic terms, the maple syrup business doesn't add up to much. The estimated 2,000 producers scattered across Vermont deliver between 400,000 and 500,000 gallons of syrup a year, generating $20m (£10m) of retail sales. Even the overall value of the industry to the state's economy of $200m (£100m) is small - far less than that of the boutique ice cream manufacturer Ben and Jerry's, another of the state's gastronomic titans (along with Vermont's exceptionally tasty cheddar cheese).

But as a symbol of Vermont, nothing can match the maple.

The tree can live up to 400 years. Some of those that are still yielding sap were probably around when the first European colonists arrived in Vermont - and were nourishing humans long before that. The Europeans learnt the mysteries of the maple from the local Iroquois and Algonquin Indians. The latter knew how to turn the sap into small black cakes for food. Indeed, some scientists say, the tree provided up to 25 per cent of their calorific intake during the harsh New England winter.

Thus were born the "sugar houses" - the shacks and outbuildings where individual syrup producers boiled the sap down into syrup. They too have entered Vermont lore. "Being in a sugar house when they were boiling was a magical experience," remembers Catherine Stevens, the marketing director of the Vermont Maple Sugar Makers' Association. "The steam made it like a sugar sauna. The old sap buckets, the pictures of grandfather on the wall, gave you this wonderful sense of history."

Up to a point, 21st century technology has caught up with maple syrup production. Gone, largely, are the buckets under individual tap holes in the trunk of a tree. Sugar bushes - the stands of trees from which sap is extracted - are now festooned with coloured plastic vacuum tubes carrying the fluid to a central collection point. You can still find horse-drawn sleighs ferrying containers of sap to the sugar houses.

Once inside however, the sap is increasingly subjected to the fancy modern process of reverse osmosis to eliminate a large quantity of water from the sap.

Thereafter, old iron boilers have given way to shiny metal contraptions with digital gauges and the like. But at heart this remains an artisanal industry - one with an especially venerable place in the history of North American agriculture.

Maple syrup, produced in the month before the onset of spring proper, is the first crop to be naturally harvested in the year. And which natural foodstuff has the oldest domestic producers' organisation in the US? Midwestern corn or wheat, or Florida oranges? Wrong. The answer, almost certainly, is maple syrup, dating back to the 1890s.

And the basics of the business haven't changed much since. Now as then, the sap only flows when the temperature at night drops to about -6C and rises to about 4C during the day. A large mature tree will probably have two taps. In an average season, each tap will yield 20 gallons of sap. When it leaves the tree, it tastes like faintly sweetened water, with a sugar content of only 2 or 3 per cent. In the sugar house the water is boiled off, until the concentration reaches 66 per cent, at which point it is genuine, waffle-worthy maple syrup.

The syrup's colour can range from a pale translucent orange-yellow to dark amber. The rule of thumb is, the later in the season, the darker the colour.

The weather is also a factor, as is the soil, and what can only be described as the mood of the individual tree on the particular day the sap is collected. No additives or preservatives of any kind are permitted. You think of Germany's reinheitsgesetz or "purity law," for beer, which states that water, hops and barley are the only permitted ingredients.

Thus it is with Vermont Maple Syrup. The term means precisely that: maple syrup and nothing but maple syrup, produced exclusively and solely in Vermont.

The state jealously protects both label and standards. Once upon a time the joke ran that more maple was made in Chicago than Vermont. But no more.

"This is our signature crop," says Henry Marckres, of the Vermont Agriculture Board, the official who is in charge of hunting down counterfeiters.

"Once in Alabama we found some people who were selling a derivative of sorghum molasses as Vermont maple syrup - and some of them ended up in prison." Given that the real thing sells for $40 or $50 (£20-£25) a gallon, and that demand for maple syrup (as for most high end food products) continues to grow, the temptation to fake it is obvious.

But now Vermont must cope with the more insidious threat of climate change. The trick for producers is divining exactly when the season will start.

Traditionally, however, harvesting begins around Town Meeting Day, the first Tuesday in March (when liberal and peace-loving Vermonters have lately have been indulging in another favoured pursuit, of passing local motions demanding the impeachment of President George Bush). Now global warming is upsetting that hallowed calendar.

"A dozen years ago we started hearing from producers they were tapping earlier and making syrup earlier," says Tim Perkins, director of the University of Vermont's Proctor Maple Research Centre, probably the world's pre-eminent seat of learning on the habits of the sugar maple. "So we scoured the records and found that over 40 years, between 1963 and 2003 the opening of the season had moved forward by an average of a week in New England." More importantly, the end of the season - when the buds start swelling and maples set about the serious business of producing leaves - now comes 10 days earlier.

"So the season now lasts three days less. It doesn't sound like much. But if you reckon that the season lasts 30 days, we've lost 10 per cent of the season in 40 years," Mr Perkins says.

In the short term, the beneficiary will be Quebec province, across the Canadian border, where a warmer, and therefore longer, summer growing season will mean bigger trees that produce more sap.

Canada already has surged ahead as a syrup producer, accounting for 80 per cent of the world's production compared to 20 per cent for the US.

One non-climate related factor has been the lavish subsidies from the Ottawa government, encouraging Canadian farmers to cultivate sugar maples. But nature has been a powerful ally. In the longer run, Vermont risks losing its maples, as flora and fauna from more southern zones encroach ever further north.

"Maple syrup production is a very sensitive indicator, depending entirely on freeze and thaw. In a few centuries, the sugar maple may only account for 10 per cent of hardwood trees in Vermont, against 50 per cent today," Mr Perkins warns. "Some computer models even show it may be wiped out entirely."

Climate change wasn't much in evidence in Vermont early this week.April was only 10 days away, but a foot and a half of snow lay on the fields and forests, and more was in the forecast.

A couple of weeks into the season, the day temperature still hovered around freezing, making sap collection impossible. Sugarhouses, old and new alike, were idle.

"Don't be fooled however," the maple research centre experts warned me. "It may not feel like it today, but this winter has been hotter than average. Some days in January the temperature was in the 60s [15C] - in Vermont!"

Some producers were tapping almost two months early. In New England, so conscious of the historical ties that bind, such aberrations are cause not for celebration, but trepidation.

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