The spread and impact of Pinus contorta in Iceland
Pinus contorta (Pinaceae) is a fast growing pine which can produce good quality timber in regions which are suboptimal for many tree species used for timber production. Native to western North America, P. contorta has been introduced to the EPPO region, New Zealand, and South America where it is reported as invasive in some regions. In Iceland, it has been widely planted since the beginning of the 20th century. In the natural area of the Steinadalur valley (south-east part of the island), the distribution of P. contorta has been mapped since 1985. Between 2010 and 2021, the distribution of P. contorta has increased tenfold from 0.25 km2 in 2010 to 2.39 km2 in 2021. The mean annual spread rate of P. contorta increased significantly, from 8.5 ± 2.4 m per year between 1985–2010 to 61.6 ± 40.2 m per year between 2010–2021. Local rates of spread also shifted, with minimum rates rising from 3.4 m/year in 2010 to 8.3 m/year in 2021, and maximum rates increasing from 13.4 m/year to 119.3 m/year over the same period. Elevational spread was also shown, with the highest recorded elevation rising from 70 m in 1985 to 116 m in 2010, and 170 m in 2021. As the population has expanded it has invaded natural heathland and birch forests reducing native plant species richness and diversity. This spread into natural areas can have potential impacts at higher trophic levels, including bird populations, where breeding sites can be lost. Managing the spread of P. contorta from plantations and in areas of high conservation should be implemented to avoid the loss of biodiversity and ecosystem services.
Sources
Wasowicz P, Óskarsdóttir G, Þórhallsdóttir ÞE (2025) Lodgepole pine (Pinus contorta Douglas ex Loudon) invasion in subarctic Iceland: evidence from a long-term study. NeoBiota 97, 47–66.