Ecology and consequences of invasion by non-native (wilding) conifers in New Zealand

Abstract

Invasion by non-native woody species into largely treeless vegetation such as grasslands and shrublands is widespread, and has prompted both research and management in response. Here I review the current situation of invasions by non-native Pinaceae, better known as ‘wilding conifers’ in New Zealand, and how both research and management are working to better understand and manage these invaders. The success of wildings is explained by a combination of history (e.g., deforestation of previously woody vegetation), biological traits of the species (rapid growth and early reproduction), and propagule pressure (introduction effort). Wildings represent a major land use change affecting about 2 million ha, including many grasslands, rare ecosystems and subalpine habitats. Wilding invasions into grasslands have profound impacts on biological diversity, but also have important ecosystem impacts including legacy effects belowground by altering nutrient cycling and soil biota. Recent expanded efforts are underway to control and co-ordinate management to avoid or mitigate the negative impacts of wilding conifers. The long-term value of managing invasions, and whether additional management interventions are needed to restore grasslands or woody vegetation is in progress, but is urgently needed given recent moves to widely establish new woody vegetation at large scales in New Zealand.