How do the orchards impact climate change and how can we help farmers prepare for a changing climate?
The orchard's contribution to climate change is determined by its impact on global atmospheric carbon dioxide equivalents. On the one hand carbon dioxide is being removed from the atmospheric system and locked-up in the growing biomass of trees and the accumulation of organic matter in the soil. On the other, it is being emitted through the burning of fossil fuels in the machinery used to run, maintain & harvest the fruit.
Some orchards have grazing animals, so where this occurs we have added the impact of methane (another greenhouse gas), which is produced in the orchard through the digestive processes of ruminants grazing there. This has a very strong impact, some 21 times more damaging than the equivalent volume of carbon dioxide.
The net benefit against climate change is the annual volume of carbon dioxide (equivalents) removed from the global system minus that emitted. We valued the total external costs of carbon dioxide using the conclusion of the Stern Review The economics of climate change that one tonne of CO 2 has an social cost of at least $85 (£45).
Having recognised through this work the importance of orchards for climate change, we commissioned Bangor University to do some evaluation of the total amount of carbon currently stored in each of the orchards. Large amounts of carbon are stored in the trees and untilled soil beneath the orchards. The findings from their report An estimate of carbon storage in orchards in Herefordshire appear to be very significant at a time when the news is about the trade-off between growing food or biofuel, since it appears that orchards are a win-win - producing food or drink AND protecting against climate change.
This chart shows the estimated carbon stored per hectare across the orchards in the project (VPGI=Village Plum, SBG=Salt Box Garnons, Tidn=Tidnor Wood, HeH=Henhope, HaH=Half Hide, BL=Bodenham Lake) Note: R=Romulus, a bush orchard right alongside Half Hide and evaluated for direct comparison.
Due to their long lives, orchards are susceptible to climate change. We have funded the preparation of an orchard factsheet published in the excellent existing Farming Futures factsheet series [ www.farmingfutures.co.uk ] which aims to help farmers start to consider the implications of climate change, what changes they might expect and how they might mitigate or exploit these changes.