Current knowledge and potential impacts of climate change on New Zealand's biological heritage

While global climate change is impacting biota across the world, New Zealand’s maritime climate is highly variable and relatively mild, so climate change is sometimes seen as a minimal threat to species and ecosystems especially in comparison to the more immediate threat of invasive species. However, climate change will alter rainfall patterns, increase the incidence and severity of extreme events, and gradually increase temperatures which will all modify terrestrial, freshwater, and marine systems. Our comprehensive review of reported climate change impacts in New Zealand indicates that most measured impacts to date are due to indirect impacts (such as exacerbation of invasive species impacts) and most are in the marine realm. Ocean acidification and marine heatwaves are particularly problematic for calcareous organisms and algae respectively. Other notable impacts include thermal squeeze in the alpine zone and impacts of drought on freshwater fish. Very small populations of rare and threatened species can be very vulnerable to extreme events (e.g. fire, floods). While the evidence for climate change impacts is sparse in some regions and for some ecosystems, we encourage ongoing monitoring to identify processes of decline that may need to be mitigated. We identify five key research needs to improve our understanding of the threat of climate change to the biodiversity of Aotearoa New Zealand.