Climate change and the fate of New Zealand’s forests

By storing carbon in wood, forests currently play a key role in mitigating climate change. However, there is growing concern that as climate changes forests could shift from being a net carbon sink to a source. In our recent paper published in Global Change Biology we explore the consequences of climate change on wood production in New Zealand’s forests.

Using repeat census data from 1070 permanent forests plots, we looked at how wood production changes over temperature and rainfall gradient across New Zealand, and then use this information to predict how climate change will affect forest carbon dynamics in the near future. We find that climate influences wood production both directly, by driving physiological responses at the tree level, and indirectly, by determining the composition and structure of forests. If the composition and structure of New Zealand’s forests were to remain unchanged over the next 30 years, then wood production would increase by 6–23%, primarily as a result of physiological responses to warmer temperatures. However, if warmth-demanding trees were able to migrate into currently cooler areas and if denser canopies were able to form, then a different response is likely: forests growing in the cool mountain environments would show a 30% increase in wood production, while those in the lowland would hardly respond. We conclude that response of wood production to anthropogenic climate change is not only dependent on the physiological responses of individual trees, but is highly contingent on whether forests adjust in composition and structure.

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