NZ peat bogs reveal climate history

New Zealand’s ancient peat bogs may hold the key to understanding how the climate has changed in the past 10 000 years and how it may change in the future according to a team of scientists from Victoria University and the University of Exeter in the United Kingdom.

The scientists spent November 2012 travelling the length of New Zealand examining peat bog ecosystems from Tāngonge Wetland just west of Kaitaia in the Far North to Invercargill’s Ōtautau Bog in Southland. They took plant and water samples and sediment drill cores representing many thousands of years of gradually accumulated peat.

Isotopes in wire rush plant tissues

The team included Professor Rewi Newnham, a physical geographer at Victoria University, and Professor Dan Charman and Dr Matt Amesbury from the University of Exeter in the UK. The researchers are particularly interested in a plant that grows in bogs, the wire rush Empodisma. They will be examining the isotopes captured in the plant tissues of samples they collected to see how the plant incorporates a record of climate into its tissues as it grows, dies and eventually forms the peat that the bogs are made of.

“We want to see whether the oxygen isotopes in roots and shoots of the wire rush and the water sources it uses to grow reflect spatial (throughout New Zealand) and temporal (over the course of a year) variation in the oxygen isotopes in rainfall. We also want to understand whether the carbon isotopes are influenced by the moisture status of the bog, reflecting the amount of rainfall received in the past. If we can figure all of this out, it means we might be able to use isotope records from wire rush dominated peat cores to study past changes in precipitation – something that’s currently very difficult to do in New Zealand,” writes Dr Amesbury in his bog blog.

At Kopuatai Bog in the Hauraki Plains near Paeroa, New Zealand’s largest peat bog, the team were assisted by Jordan Goodrich, a PhD student from nearby University of Waikato, who is working on the site measuring gas fluxes.

The research was funded by the UK’s Natural Environment Research Council.

Past climates

Past climate can be studied in a number of ways by examining environments that hold a record of past changes. These environments include ice cores, tree rings (including fossilised trees), the growth rate of stalagmites in caves and sediments laid down over time in the bottom of lakes or in peat bogs.