Royal Society paper highlights freshwater usage as a global issue, rivaling greenhouse gas emissions

11 September 2009

Download the full paper:

• Emerging Issues - Virtual Water (PDF, 728 kB)

Listen to an online briefing of journalists about Virtual Water from the Science Media Centre:

• Science Media Centre: Virtual water - what is it, and what does it mean for NZ?

The amount of freshwater used to produce agricultural goods and services is a growing issue for New Zealand, according to a paper released by the Royal Society of New Zealand.

In its paper the Royal Society says this water usage, measured as ‘virtual water’, will become as important a global issue in the future as greenhouse gas emissions.

Dr Brent Clothier, an environmental scientist with Plant & Food Research who contributed to the paper, says that in New Zealand three quarters of the water taken from our resources is for agricultural purposes.

“Because we export a high proportion of our agricultural production, we are effectively a major exporter of virtual water.”

Virtual water is a measure of the water use required to produce a product or service. A cup of coffee can take around 140 litres of water to produce, mostly to irrigate the coffee plant. A hamburger can require 2400 litres, using global average figures.

Current figures show that New Zealand is in the top three exporters of virtual water per capita, behind Australia and Canada.

Dr Clothier says many organisations internationally are now developing measures for sustainable water use. New Zealand farmers will increasingly be required to show that their water usage meets these standards.

“At present we really don’t have accurate data about the virtual water content of our agricultural products. Our farmers are also a long way from being able to certifiably report on the social and environmental impacts of their water usage,” says Dr Clothier.

Recent reports by the business consultancy JP Morgan and the World Wide Fund for Nature have flagged the overseas water footprint of the UK and other European nations as an issue of concern. Some 62% of the water ‘consumed’ in the UK comes in as virtual water in imported products.

“Sensitivity around water usage comes on top of issues like carbon footprinting. In the future we may have to prove the water efficiency of our agriculture in order to maintain trade ties,” says Dr Clothier.

The Royal Society paper says the key issue is not the level of water usage but the impact of its use and this differs between products, countries and regions within countries.

For example, freshwater in New Zealand is far more available than in southern Australia, so water used for irrigation has different environmental and social impacts in the two countries.

“To develop and export sustainable food and drink, New Zealand needs measures of the impacts of water use, not just the amount of water use,” says Dr Clothier.

The Royal Society paper concludes that New Zealand’s agricultural water use may well be ‘a major trade advantage’ if we can measure water footprints and demonstrate environmental stewardship. It could also be a ‘possible trade risk’ depending on how the virtual water concept is used to measure sustainability.

It says that measuring the virtual water content of our products is a ‘necessary first step’ to improving and demonstrating our efficiency and performance. Many of the techniques to improve irrigation efficiency and reduce virtual water contents are already known. The challenge lies in improving irrigation practices so that water is being used effectively and not wasted.

Dr Clothier says this is a treble win as farmers will also save costs and reduce their carbon footprint at the same time.

The paper also says international debate around water sustainability is lagging around five to ten years behind the carbon footprinting debate, but that this debate will ‘become unavoidable’ as we increasingly become a water-constrained world.

For further information:

Jez Weston, Royal Society of New Zealand, Ph 04 470 5792, Mob 021 444 897, Email: jez.weston@royalsociety.org.nz

Dr Brent Clothier (available until 15 September), Ph 06 953 7687, Mob 021 226 8687, Email: brent.clothier@plantandfood.co.nz On mobile after 15 September (with 5hr time difference).

Philippa Sargent, communications advisor, Royal Society of New Zealand, Ph 04 470 5807, Mob 027 697 4940, Email: philippa.sargent@royalsociety.org.nz