This indicator compares actual harvest levels against what is deemed to be sustainable. The purpose is to assess where forests are being harvested beyond their ability to renew themselves or are being under-utilised for wood products.
New Zealand planted forests are dominated by radiata pine (90 percent) and Douglas-fir (6 percent). The volume of wood harvested annually is estimated from the quantities of processed wood products and export log volumes. For planted forests, most of which are now in private ownership, the annual volume of wood that can be harvested is not prescribed by any central agency. Standing volumes have increased steadily over recent years, and this growth is expected to continue as more forestry plantings reach maturity. Harvested volumes have also increased, but at a slower rate.
To assist with forest industry planning, the Ministry for Primary Industries (formerly the Ministry of Agriculture and Forestry) has compiled regional wood availability forecasts for radiata pine and Douglas-fir. These were produced with the assistance of major forest growers and industry consultants. They cover the period from 2008 to 2040. Minor planted forest species have not been included because of their insignificance to the overall wood supply.
The national forecasts presented here are the sum of the regional forecasts. Four scenarios are provided for radiata pine and one for Douglas-fir. The modelling uses the age class distribution of the forests and the harvesting intentions of the large-scale forest owners (> 1000 hectares of forest) for the first 10 years to estimate an expected harvested wood volume for each year.
The following are the four scenarios applied to radiata pine:
Scenario 1 assumes all owners will harvest their forests when their forests reach the age of 30 years. This scenario shows the unconstrained availability of radiata pine from New Zealand planted forests.
Scenario 2 assumes large-scale owners will harvest in line with their stated intentions, and small-scale owners will harvest their forests at age 30.
Scenario 3 assumes a non-declining yield, with a target rotation age of 30 years. Under this scenario, the potentially available volume increases to over 30 million cubic metres per year from 2020.
Scenario 4 is the same as for scenario 3 except that total wood availability is allowed to decrease from 2034 (the end of the current rotation). Wood availability increases to over 35 million cubic metres per year from 2022 before reducing to 28 million cubic metres per year from 2037.
It should be noted that while Scenarios 1 and 2 are theoretically possible, they are unlikely to be realised because New Zealand does not have the infrastructure capacity to deal with the rapid rise in wood volumes forecast for the mid 2020s.
Available Douglas-fir wood is forecast to remain below 1 million cubic metres per annum through to 2024, and to have increased to 2.5 million cubic metres per annum by 2040.