Hills covered in ideal fuel for wildfires

The gorse, grass and pines on the Port Hills above Christchurch are among ideal plants to fuel the wildfires sweeping through the area.

“The Port Hills and Banks Peninsula have large tracts of continuous, highly flammable vegetation,” said Dr Tim Curran, senior lecturer in ecology at Lincoln University, yesterday.

“This includes scrub dominated by gorse, pine and eucalypt plantations or shelterbelts, pastures and grasslands, and native regrowth dominated by kanuka,” Curran told the Science Media Centre.

“When combined with hot, dry and windy weather, such vegetation fuels the intense and extensive fires like those . . . on the Port Hills.”

The key vegetation factors that determine the behaviour of a fire are:

● The biomass (the amount of plant material),

● Its layout (how continuous or connected the vegetation is), and

● The flammability (how well it burns).

Other factors are the weather and the topography: fires spread with the wind and uphill as flames are tilted towards the fresh fuel.

University of Auckland professor of environmental science George Perry said thin, dead plants such as grasses were highly combustible because of their low moisture content and how fast they dried.

“The vegetation on much of the Port Hills is extremely flammable, especially in those areas where gorse, which is characterised by large amounts of well-connected, dead and fine material, is abundant.”

Perry urges Kiwis to look at ways to reduce our risk of fire such as using “green fire breaks” — plantings of less flammable trees. — Martin Johnston