Leaves collected on Captain Cook’s 1769 voyage show CO2 shift in New Zealand’s atmosphere
Density and porousness from 250-year-old leaves compared with the current samples of same species
By Jamie Morton
Leaves once collected during Captain Cook’s first voyage to New Zealand, nearly 250 years ago, have helped scientists measure an increase in carbon dioxide (CO2) in our atmosphere.
The researchers, at Unitec Institute of Technology, have compared historic samples of karaka with leaves today to investigate any change in density of microscopic pores, called stomata.
Links have been shown between the levels of CO2 in the surrounding atmosphere and the density of stomata on certain plants, and these historic herbarium specimens provided a unique opportunity to see what plants were like before the rise in atmospheric CO2 levels.
Stomata regulated the intake or release of (CO2), oxygen, and water vapour.
Plants required carbon dioxide for photosynthesis — the process by which they make food — and were known to decrease the number of pores in response to higher amounts of CO2.