The fundamental unit of agricultural productivity is the health of the soil. The soil mediates and takes part in many global processes, cycling water, nutrients and carbon. It does this by hosting millions of species of micro-organisms, which drive these processes.
Intensive agriculture has in many parts of the world desecrated the health of the soil and the populations of soil microbes. With poor soils, it is difficult to grow anything sustainably, and the more fertilisers, pesticides and irrigation water is required. Agro-chemicals are becoming more costly, but less effective. At the same time, pollution from agricultural runoff is having consequences in watercourses and even the ocean, by causing eutrophication. Soils and intensive agricultural practices have little natural resilience to droughts or floods, and this is particularly relevant with climate change.
Floods and drought, climate change, water pollution, water resources and wastewater treatment, biodiversity, and agriculture can all be resolved to mutual benefit.
Naturalistic solutions to water problems can be provided at benefit to biodiversity and agriculture. Examples of this include principles taken from Biodynamic farming, Permaculture, Microbial Balancing or from the Australian Keyline Plan (written by Yeomans). These sensitive alternatives to intensive farming recognise the inter-connectedness of the ecosystems, and they promote a healthy ecosystem (from catchment-wide habitats, down to the micro-habitat of soil bacteria and fungi). In doing so, the water cycle is a major component of the approaches, bringing the many additional benefits already mentioned.
Yeomans, K. B. (2008) Water for every farm: Yeomans Keyline Plan, Queensland: Keyline Designs.