Agriculture Reference
In-Depth Information
water in agriculture little else matters - including
use of land, energy, improved or favourable
biodiversity, or reduced contamination of water
and air. Freshwater is an increasingly scarce
resource in many regions of the world (Pimentel
et al
., 2004; Rosegrant
et al
., 2009). Among
many other uses, it has an especially important
role in animal agriculture and sustainability.
However, it has not been studied and assessed as
much in animal systems compared with plant
systems. Water obviously is essential for all life.
However, different organisms (e.g. animals ver-
sus plants) and different production systems
dictate vastly different quantities (footprints)
and efficiencies of water use (Rosegrant
et al
.,
2009; Hanasaki
et al
., 2010; Hoekstra, 2010).
Although water is no more precious to animal
than to plant agriculture, some current animal
production practices and systems especially in
developed or rapidly developing countries will
not be practical or even possible in sustainable
animal agriculture systems in the next 50 years.
It is widely known that production of animal
products in some systems is very water-intensive
(Chapagain and Hoekstra, 2003; Pimentel
et al
.,
2004; Raman, 2006; Herrero
et al
., 2009).
About two-thirds of all human water usage
between 2000 and 2010 was to irrigate crops
for food-feed production (Strzepek and Boehlert,
2010). Of that, about one-third of the total
water footprint was associated with the produc-
tion of animal products, mainly utilizing water
to grow livestock feed (Mekonnen and Hoekstra,
2012). Also, as a consequence of global warm-
ing, changes in availability and distribution of
water supplies are occurring (Strzepek and
Boehlert, 2010). From modelling efforts,
Strzepek and Boehlert (2010) predicted an 18%
reduction in global water availability for agricul-
ture by 2050. This will result in large part from
the environmental flow requirements (freshwa-
ter needed to maintain natural riparian ecosys-
tems), plus increased demands for municipal
and industrial uses (two-fold increase in devel-
oping countries), and altered timing, distribu-
tion and supply of water due to climate change.
The combined effects are projected severe water
shortages in much of Asia, northern Africa,
parts of Europe, eastern Australia and much of
the western half of the USA.
Although the world's agriculture system
will need to produce more food for an expanding
and presumably wealthier population in the dec-
ades ahead (Steinfeld
et al
., 2006; Janzen, 2011),
the increasing demands for freshwater and
potential impacts of climate change represent
formidable threats to food and feed production
for humans and animal agriculture. This will be
further accentuated and stressed by practices in
some animal production systems that are very
water-intensive and likely will make these prac-
tices unsustainable in the not too distant future.
Recent research by Mekonnen and Hoekstra
(2012) made a concerted effort to characterize
and project the water footprints of various
human-edible food products (of both plant and
animal origin) on a nutritionally equivalent
basis (protein, fat and energy), and also to con-
sider the amounts and compositions of feedstuffs
consumed per animal species in different farm-
ing system types (grazing, mixed and industrial)
in four countries (China, India, the Netherlands
and the USA). Water footprint was defined as the
amount of water required to produce a unit of
animal product from farm to fork, including
water requirements to grow the different feeds
that the animals consumed. The predictions also
were compared with footprints for production of
several plant crops. As a general conclusion in
terms of use of freshwater, it was more efficient
to obtain calories, protein and fat from produc-
tion of crops than from animal products. The
water footprint of any animal product was
greater than the water footprint of any edible
crop on an equivalent nutritional (protein or
caloric) basis. For example, the most dramatic
contrast was the water footprint per calorie of
beef at about 20 times greater than for cereals
and starchy roots. The water footprint per gram
of edible protein from milk, eggs and chicken
meat was about 1.5 times greater than for dry
beans. However, the more specific nutritional
quality of the protein (e.g. the profile and
amounts of the dietary essential amino acids
from different animal or crop food products) and
fats (e.g. dietary essential fatty acids) was not
considered in their analysis. Perhaps this would
be a useful characterization and comparison,
particularly applicable for parts of the world
where deficiencies of high-quality dietary pro-
tein are a serious problem.
The overall greater water footprints of ani-
mal compared with plant products are due in
significant part to the unfavourable conversion
