The Nexus Approach to Managing Water, Soil and Waste under Changing Climate and Growing Demands on Natural Resources - Governing the Nexus: Water, Soil and Waste Resources Considering Global Change - page 47

especially important in rapidly developing economies such as China (Mu and Khan
2009 ). Further, 60 % of the global population may suffer from water scarcity by
2025 (Qadir et al. 2007 ). Thus, identi

cation of non-conventional water resources
(e.g., grey water, desalination of seawater) is crucial to the wellbeing of the pop-
ulation in arid regions. The importance of water-saving techniques and increasing
water productivity cannot be over emphasized (Hamdy et al. 2003 ). In this context,
there is an urgent need for rethinking of virtual water with regards to global food
trade and policy perspective (Kumar and Singh 2005 ). Thus, the nexus approach is
critical to advancing food security in the water-scarce world.

4 Linking the S-W-S Nexus Approach to Urban
Agriculture

Most of the land suitable for crop production is already being cultivated. Unused
land exists in regions that are too dry, too wet, too cold, too hot or otherwise
inaccessible. Further, some of the potentially available land exists in ecologically-
sensitive ecoregions (e.g., tropical rainforests). Yet, the per capita arable land area
has decreased to about 2,500 m 2

cation to
narrow the yield gap in developing countries (e.g., Sub-Saharan African, South
Asia, the Caribbean, Andean region) is needed and must be pursued, there are
ecological limits to what can be achieved. The soil-less agriculture is not a new
concept, and it has been used in research for decades throughout the twentieth
century. The soil-less culture refers to

(0.25 ha). Whereas sustainable intensi

“ an arti cial means of providing plants with

support and a reservoir of nutrients and water (Johnson et al. 1985 ). There are

several types of soil-less cultures. Floating gardens, a form of hydroponics, has
been used in South Asia (Haq and Nawaz 2009 ; Irfanullah et al. 2011 ; Wikipedia
2013 ) and Central America (Squier 1851 ). The

”

floating islands
constructed from mud and plants, were used by Aztecs to grow crops. Aztecs
expanded the city

“ Chinampas, ” small

s land surface to cover more than 12.5 km 2 or 5 square miles. 1

'

Nonetheless, floating gardens now constitute modern technology (Sweat et al.

2013 ).
Traditionally, urban agriculture (UA) involves conversion of abandoned land
previously under homes, buildings and parking lots, etc. into agricultural land for
production of vegetables and other short-season horticulture crops (Lal and
Augustine 2011 ). To reduce food mileage and recycle nutrients in human waste,
there is a growing interest in modern UA. It is also called skyfarming or vertical
farming. Skyfarming is an innovative option of enhancing food production by
utilizing the food-waste nexus in urban ecosystems and involves indoor crop pro-
duction within purpose-built multi-storey buildings (Germer et al. 2011 ; Fischetti
2008 ). It minimizes resource use (land, water, nutrients) per unit of crop production,

1

For more information, see http://www.instructables.com/id/Build-an-Aztec-Water-Garden/ .