Environment – Changes are a coming

Climate change is coming and maybe faster than you think. The predicted changes could have big impacts on the future biodiversity on islands like Tiritiri Matangi.

In recent news it was reported that NIWA have just completed a year-long high-resolution modelling run which predicts the expected climate change over various future time periods for a range of emission scenarios. The results are available on the Ministry for the Environment’s website, and they intend to allow users to generate and view the data superimposed on maps. Until those are available, we have the results from NIWAs Auckland Region Climate Change Projections and Impacts published in 2018.

For an emissions as usual model (no reductions in CO₂ emissions) this report suggests that (compared to 1995 values) by 2040 we can expect the mean annual temperature to increase by 0.8^oc an extra 15 to 20 days each year when the temperature is above 25^oc, increases in evapotranspiration (leading to dryer soils), three to nine more dry days, increases in severe rainfall events and about 30 cm of sea level rise. 

These figures should be considered worst case as we are expecting some reductions in CO₂ emissions. But they are certainly possible and could have a significant impact on Tiritiri Matangi and everywhere else of course, and 2040 is just 16 years away. A hotter, drier climate with less soil moisture is likely to change which trees and other plants will continue to thrive on the island and which may not survive. Mahoe/whiteywood, one of our commonest trees and a great food source for birds, reptiles and invertebrates, already suffers in dry summers with some dying in prolonged dry spells. We have seven reptile species on the island, and most will only do well while the range of temperature, soil moisture and plant species remain suitable. Year-round supplies of nectar are important for some of our birds and changing climate may impact on the timing and quantities of food available. We can also expect new weeds to continue to appear.

So, climate change presents a risk to the future of the island and its plants and animals. We need to consider those risks and to plan for them. One way to do this is to identify coastal areas in New Zealand which currently experience the predicted changed conditions and to compare which plants and animals are present there. We can also use our experience of which plants and animals seem to be able to withstand hot, dry summers and which cannot. 

Planning for the future has become more complex. We probably need to change our goals for the forest and for future animal translocations.