environment

A billion new trees in a warming world

While California smoulders, New Zealand researchers are figuring out ways to reduce the fire risk a billion trees pose in a warming world. Farah Hancock reports.

When Tim Curran arrived at Lincoln University from Australia the first piece of equipment he asked for was a barbecue.

He wasn’t planning to throw a prawn on it. The barbecue, purpose-built out of a 44-gallon drum, is essential to the ecologist’s research into the flammability of different plants.

It’s a low-tech tool to understand a growing risk. Climate change means the number of days where the risk of fire is classed as very high or extreme are expected to increase by 71 percent in New Zealand by 2040.

With the One Billion Trees programme adding more fuel to the countryside his work represents the life and death importance of finding the right tree for the right place.

All trees will burn, but some burn faster and hotter than others. Curran’s barbecue weeds out the fierce burners.

“It would be best if you could burn a whole plant, which is fine if you are dealing with a grass, it’s harder for a shrub and it’s pretty much impossible for a tree,” said Curran.

His solution is to burn 70cm shoots in his barbecue.

“That retains the leaves in the architecture they are found in on the plant. It ensures the fuel [shoot] is a bit more realistic as to how it might burn in the field.”

Once on the barbecue, readings are taken measuring how quickly the shoot ignites, how long it burns for and the temperature it burns at.

Typically, the more moisture the plant has in its leaves, the less flammable it is. Another factor is how much oil or resin a plant has.

“In general, pine species are going to be quite high in flammability because they’ve got some of these volatile chemicals. The pine resins and other things you smell when you walk through a pine forest are some of the things that ignite easily in a fire.”

“If you think about a campfire, you don’t stack all your firewood immediately next to the fire. You keep a bit of a fuel break between your campfire and whatever logs or material you have.”

Some native species such as tree fuchsia aren’t very flammable. Others including mānuka and kānuka are highly flammable.

“They’re fantastic native species and incredibly useful plants, so we should be using them, but they do come with an added risk of being highly flammable. If you’ve got a big unbroken patch of mānuka or kānuka there’s a bigger chance a fire might actually go through the entire planting and kill all the plants in there.”

It’s not just lives and livelihoods at stake if plantations go up in smoke. A key driver of the One Billion Trees programme is carbon sequestration. Burning trees become a carbon source instead of a carbon sink.

Curran uses a rugby analogy to explain the impact: “It's like a 14-point turnaround, where your team is attacking your opponent's try line and looking certain to score, and the defending team gets a turnover or intercept and scores up the other end. Instead of potentially going seven points up, you are now seven points down. A 14-point turnaround.”

A changing climate

Climate change is predicted to increase the risk of conditions where flammable plants are at their most likely to burn fiercely.

Curran gave the example of California’s fires where the area has “unprecedented vegetation dryness” for this time of the year.

“Here in New Zealand the predictions for climate change are things like hotter temperatures, less rainfall, more drought, lower humidity and windier conditions in many parts of the country, particularly the eastern parts of both islands.

“Put very simply, if you’ve got hotter temperatures, if you’ve got windier conditions, if you’ve got drier conditions all of those things are going to make for a better fire. Your fuel is going to burn more extensively, it’s going to burn hotter, you’re going to get more extreme fires.”

Predictions made in a recent paper from SCION modelling the effects of climate change on plantation forests show how this could play out by 2090.

“We can’t change the weather on a given day. We can’t change topography, but we can change fuel loads.”

Christchurch, where the Port Hills were engulfed in flames containing energy equivalent to four atom bombs, will experience up to 10 more days per year where the risk levels reach the worrying “very high or extreme” level. Gisborne faces a similar increase.

Places where the risk has traditionally been low will need to adjust to increased fire risk.

By 2090 Dunedin will face a 207 percent increase in days of very high or extreme fire risk per year, while Wellington will see an 89 percent increase.

Fuel for the flames

“We can’t change the weather on a given day. We can’t change topography, but we can change fuel loads.”

The Billion Trees programme is likely to add up to a million more hectares of fuel to New Zealand’s landscape. Planting lower flammability trees is one way of reducing fire risk, another is breaking up plantings.

“If you think about a campfire, you don’t stack all your firewood immediately next to the fire. You keep a bit of a fuel break between your campfire and whatever logs or material you have.”

Curran’s team are looking at green fire breaks. These are strips of low flammability plants placed at strategic points. They could break up areas of highly flammable vegetation or be used to surround buildings and either slow down or stop fire. Embers blown on to the low flammability plants don't ignite, and the break can act as a heat barrier preventing the next block of trees, or structure heating to a point where it becomes more flammable.

China is the world leader in green fire breaks. Already it has planted 364,000km of them and it is planning to plant another 167,000km by 2025. One of Curran's students is translating Chinese research into green fire breaks which suggests high intensity fires can be stopped by a 10-metre-wide green fire breaks. Curran cautions no research has been done to understand the upper limit where green fire breaks will fail. It’s something he thinks needs to be looked at.

“We have to remember they are plants. Under the right conditions, say a severe drought, any plant is going to turn into fuel.

"Those tests haven’t necessarily been done under the sort of extreme conditions, say the Port Hills fire was, or certainly fires in California, or the ones you get in Australia."

The fire fighters

John Rasmussen, national manager for rural operations for The Fire and Emergency Service, said lessons were learnt from Port Hills. A new incident-managing system has been investigated and several multi-agency exercises were conducted around the country.

Work with communities is also being done to help people understand more about how to clear vegetation close to homes to reduce the risk of fire damage.

The service already works closely with the forestry industry and has done for many years. Good silviculture, fire breaks and setbacks are important, as well as access to water and ensuring tracks exist so fire crews access fires.

Rasmussen believes for the plantation industry, where growers have a vested interest in protecting a crop, good fire prevention strategies will continue even with the increase the Billion Trees programme will bring.

He hasn’t heard of large plantings of mānuka taking place.

“That’s going to pop up over the next few years. We need to be aware of that. Mānuka is highly flammable and it’s a scrub fuel type. Obviously, a fire would spread and burn pretty rigorously in that environment.”

Rasmussen said very few fires are started by non-human related causes such as lightning.

“Virtually all of the fires are caused by humans. If we can put a lot of effort into education and fire prevention then that’s probably going to be a pretty effective way of dealing with the issue.”

The One Billion Trees programme will likely result in 775 million plantation forestry trees and 225 million indigenous trees being added to New Zealand’s landscape over the next 10 years or, as Curran sees it, around a million new hectares of fuel.

Earlier this year 1.67 million mānuka seedlings were given to landowners. If combined in one planting, these would cover 1461 hectares.

“I argue for the Billion Trees programme, this excellent initiative, we need to incorporate issues such as fire hazard and plant flammability into our decision-making process when we are deciding where to put these trees,” said Curran.

“The beautiful thing with the Billion Trees programme is we are at the start of the programme.”

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