Growing ConcernsPlantation forestry in a thirsty world

One sure thing about planting a forest is that the world will be a different place when that forest is ready to harvest. The mature plantations that now make up the “wall of wood” were planted 30 years ago. At that time forestry was a minority industry, and plantations were usually confined to marginal land well out of sight and out of mind from the average New Zealander.

At that time, too, New Zealand was still relatively resource- rich. There was seemingly plenty of water for all users, and plenty of electricity generation capacity from geothermal power stations in the North Island and hydro-electric dams in the South Island.

Times have changed. The harvest from plantation forests has more than trebled over the past 30 years. Where forests once had one or two farmers as neighbours, now whole communities of lifestylers may live on the forest boundary. Increasing human population and the success of irrigated farming systems have increased demand for water to the point that even a region as rich in groundwater as Canterbury is probably approaching the limit of how much it can take from the ground without replenishment.

The increasing size of the forest industry and the increasing demands made by New Zealanders on the rural environment mean that forestry must increasingly come into conflict with other sectors of the New Zealand community. An example is the recent imposition of controls on new forestry planting in the Tasman District. These controls were designed to protect irrigators in the water-short Moutere catchment.

The science behind these controls is not in dispute. Any tall woody vegetation (such as a forest) intercepts more rainfall than a short pasture. Some of this intercepted rainfall is evaporated back into the atmosphere and never reaches the ground. Because of this evaporative loss, a mature stand of pines, native forest or brushweeds may yield 30%-40% less run-off than an equivalent grazed pasture. As a result, streams that supplied vital irrigation water may dry up to a trickle or even stop flowing altogether.

What is in dispute is whether the proposed controls are an over- reaction.

The Tasman District regulations withstood a legal challenge from the forest industry in the Environment Court. In contrast, similar proposals from the Otago Regional Council met resistance from local foresters and were dropped.

Now, Environment Canterbury is proposing to place controls on new plantations in water-short catchments in the foothills to the east of the Southern Alps. The regulations are designed to protect flows during critical periods in summer and early autumn when flows are at a minimum, while at the same time irrigators have the greatest need to take water.

Currently, Environment Canterbury proposes blanket controls on forestry in the water-short catchments. The forest industry in Canterbury argues that controls are only needed in those parts of the catchments that contribute significantly to summer low flows. In other words, regulation should be confined to those areas where pine plantings really would make a difference to the amount of water flowing in the river. It seems senseless to impose a regulatory burden on landowners in areas where planting pine trees would not make much difference.

Another issue in dispute is the relative risk to flows from plantations compared to the risk that might be posed by reversion of pastures to woody weeds or native forest. Most of the catchments proposed for regulation were forested before the arrival of humans in New Zealand. The rainfall and soils in these areas are suitable for growth of woody plants, and many a hill-country farmer can attest to the willingness with which pastures will revert to brushweeds and native forest if not managed carefully. On marginal land, plantations are often the only economic alternative to scrub reversion. Foresters argue that it seems perverse to restrict forestry in areas that are reverting to scrub because this scrub will have the same consequences for downstream river flows as if the plantations had been allowed in the first place. One reason for this anomaly is that the Resource Management Act allows councils to restrict an active land use like tree planting, but does not allow them to control a passive activity such as allowing a pasture to revert to woody weeds or native forest.

Where to from here?

We will have to work hard to ensure that forestry is regulated in a fair and non-arbitrary way. The forestry industry’s importance to the economy as an employer and as our third largest export earner does not make us special in the eyes of the average New Zealander. Irrigators, recreational users, fishermen and others are not particularly worried if forestry gets the short end in any conflict over resource use. We need to be ready to put our case as often as is required to ensure the industry gets a fair allocation of the natural resources it needs to stay viable.

* Mark Bloomberg is a lecturer in forestry at Lincoln University. He represented the NZ Institute of Forestry and other forestry interests during consultation with Environment Canterbury over proposed restrictions on forestry in water-short catchments.

The NZ Institute of Forestry was founded in 1927 as a forum for those involved in forest management, utilisation, research and consulting. With around 740 members currently, it is a professional body committed to serving the practice of forestry and the wider community through education, accountability and its codes of ethics and performance standards. For more information phone the Secretariat, 0-3-960 2432, email nzif@paradise.net.nz or visit www.nzif.org.nz