New study reveals irrigation's mixed effects around the world

Date:
June 20, 2023
Source:
New York University
Summary:
Trajectory of irrigation water use in many regions is unsustainable,
but practice is vital in managing climate change and future
agricultural development, researchers conclude.


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FULL STORY ==========================================================================
The analysis, which appears in the journal NatureReviews Earth and
Environment, also points to ways to improve assessments in order to
achieve sustainable water use and food production in the future.

"Even though irrigation covers a small fraction of the earth, it has
a significant impact on regional climate and environments -- and is
either already unsustainable, or verging on towards scarcity, in some
parts of the world," explains Sonali Shukla McDermid, an associate
professor in NYU's Department of Environmental Studies and the paper's
lead author. "But because irrigation supplies 40% of the world's food,
we need to understand the complexities of its effects so we can reap
its benefits while reducing negative consequences." Irrigation, which
is primarily used for agricultural purposes, accounts for roughly 70%
of global freshwater extractions from lakes, rivers, and other sources, amounting to 90% of the world's water usage. Previous estimates suggest
that more than 3.6 million square kilometers -- or just under 1.4 million square miles -- of the earth's land are currently irrigated. Several
regions, including the US high plains states, such as Kansas and Nebraska, California's Central Valley, the Indo-Gangetic Basin spanning several
South Asian countries, and northeastern China, are the world's most
extensively irrigated and also display among the strongest irrigation
impacts on the climate and environment.

While work exists to document some impacts of irrigation on specific
localities or regions, it's been less clear if there are consistent and
strong climate and environmental impacts across global irrigated areas --
both now and in the future.

To address this, a total of 38 researchers from the US, Australia,
Austria, Belgium, France, India, Italy, Japan, South Korea, and Taiwan
analyzed more than 200 previous studies -- an examination that captured
both present-day effects and projected future impacts.

Their review pointed to both positive and negative effects of irrigation, including the following:
* Irrigation can cool daytime temperatures substantially and can also
change how agroecosystems store and cycle carbon and nitrogen. While
this cooling can help combat heat extremes, irrigation water can
also humidify the atmosphere and can result in the release of
greenhouse gasses, such as powerful methane from rice.

* The practice annually withdraws an estimated 2,700 cubic kilometers
from
freshwater sources, or nearly 648 cubic miles, which is more water
than is held by Lake Erie and Lake Ontario combined. In many areas,
this usage has reduced water supplies, particularly groundwater,
and has also contributed to the runoff of agricultural inputs,
such as fertilizers, into water supplies.

* Irrigation can also impact precipitation in some areas, depending
on the
locale, season, and prevailing winds.

The researchers also propose ways to improve irrigation modeling --
changes that would result in methods to better assess ways to achieve sustainable water and food production into the future.

These largely center on adopting more rigorous testing of models as
well as more and better ways of identifying and reducing uncertainties associated with both the physical and chemical climate processes and -- importantly -- human decision-making. The latter could be done with more coordination and communication between scientists and water stakeholders
and decision-makers when developing irrigation models.

"Such assessments would allow scientists to more comprehensively
investigate interactions between several, simultaneously changing
conditions, such as regional climate change, biogeochemical cycling,
water resource demand, food production, and farmer household livelihoods
-- both now and in the future," observes McDermid.

This research was supported by the National Science Foundation (1752729, 2127643), the National Research Foundation of Korea, and the Japan
Science and Technology Agency.

* RELATED_TOPICS
o Plants_&_Animals
# Agriculture_and_Food # Food_and_Agriculture # Nature
# Soil_Types
o Earth_&_Climate
# Environmental_Issues # Water # Environmental_Awareness
# Climate
* RELATED_TERMS
o Water_resources o Water_scarcity o Animal_husbandry
o Global_warming_controversy o Climate o Irrigation
o Consensus_of_scientists_regarding_global_warming o
Climate_change_mitigation

========================================================================== Story Source: Materials provided by New_York_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Sonali McDermid, Mallika Nocco, Patricia Lawston-Parker, Jessica
Keune,
Yadu Pokhrel, Meha Jain, Jonas Ja"germeyr, Luca Brocca, Christian
Massari, Andrew D. Jones, Pouya Vahmani, Wim Thiery, Yi Yao, Andrew
Bell, Liang Chen, Wouter Dorigo, Naota Hanasaki, Scott Jasechko,
Min-Hui Lo, Rezaul Mahmood, Vimal Mishra, Nathaniel D. Mueller,
Dev Niyogi, Sam S.

Rabin, Lindsey Sloat, Yoshihide Wada, Luca Zappa, Fei Chen,
Benjamin I.

Cook, Hyungjun Kim, Danica Lombardozzi, Jan Polcher, Dongryeol Ryu,
Joe Santanello, Yusuke Satoh, Sonia Seneviratne, Deepti Singh,
Tokuta Yokohata. Irrigation in the Earth system. Nature Reviews
Earth & Environment, 2023; DOI: 10.1038/s43017-023-00438-5 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/06/230620113749.htm

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