Natural resource managers maintain resilient agro-ecosystems

This post is part of the Agriculture and Ecosystems Blog’s month-long series on Resilience.

The CGIAR Research Program on Water, Land and Ecosystems (WLE) aims to shift from the current paradigm of productivity (of agro-ecosystems) enhancement while reducing environmental impacts, to a paradigm where sustainability of agro-ecosystems constitutes the entry point for all agricultural development.  What does this mean to a natural resources manager?  Can WLE tell them how to operationalize this paradigm?

Groundwater can be used for agriculture even during dry periods. Photo: IWMI

Being a groundwater hydrologist, I will use examples from groundwater hydrology to make some suggestions for groundwater managers.

An agro-ecosystem system is made of several components such as cropland, wetlands, precipitation, surface water and groundwater.  The net benefits from the system are greater than can be derived from each component individually. In some systems, there is interconnectivity between components, e.g., surface water bodies recharging aquifers or groundwater contributing to base flow in rivers.

When groundwater is available:

Variable weather can impact the way in which agro-ecosystems are managed by natural resource managers.  For example, during droughts, precipitation is low which causes tanks to be short of water; but groundwater could meet evaporation demand.  With groundwater, a crop failure could be averted and a system’s resilience to drought could be retained.

However, during wet years, evaporative requirements are met, tanks are full, and groundwater is recharged.  But if natural recharge processes are inadequate, then, a natural resources manager could implement strategies to increase recharge (managed aquifer recharge), or promote water-use-efficiency measures to minimize groundwater withdrawals.  The role of the natural resources manager in this case is to ensure that the system’s surface and groundwater resources will recover and that the system remains resilient to future droughts.

When groundwater is unavailable:

In other agro-ecosystems, such as those where groundwater is saline or groundwater is too deep to access, then it is most likely that a crop will fail in drought years.  Successive droughts will endanger the system’s resilience.  In order for systems like these to remain productive and resilient, land-use has to change and less water intensive crops should be grown.

Metrics for management

The examples above illustrate strategies that may be adopted to enhance the resilience of an agro-ecosystem with and without groundwater.  In order to operationalize these strategies, natural resource managers will require metrics to determine the ‘allowable change’ of a component within a planned time period.  These metrics need to be low in ‘noise’ and ‘uncertainty’.  While doing monitoring one component, the interconnectivity among components and the impact on the system as a whole need to be monitored.

For a groundwater manager, the indicator variable may be the allowable change in groundwater levels.  For example, in the Lachlan Aquifer in NSW, Australia, groundwater managers allow 40% reduction in saturated thickness during droughts, before implementing an embargo on groundwater pumping.

These changes to groundwater levels have a temporal dimension.  The figure bellow shows the changes to groundwater levels in Bhinder District of Rajasthan, India.  The highest groundwater level was 492 m above mean sea level (msl) in January 1995, and the lowest was 467 m above msl in January 2001.  Suppose the groundwater levels recovered to 492 m above msl, then the levels have fluctuated between a bandwidth of 25 m (492-467=25).  If this has happened then we may consider this as the ‘band width of resilience of a component (groundwater)’.  If this bandwidth can be determined, excluding noise and uncertainty, it can then guide groundwater management in the district to keep levels within the bandwidth so that resilience is assured.

The figure below shows the changes to groundwater levels in Bhinder District of Rajasthan, India

But, the levels did not recover to 492 m above msl in a thirty year period.  Instead, it rose to 489 m above msl only.  The regression line indicates that there’s a decline of 18 cm/y during the 30 year period.  Again, this is probably useful information for groundwater managers to implement strategies, that will increase recharge or decrease discharge, to minimize the net decline of groundwater level by 18 cm/y.

In summary, resilience of an ecosystem will depend on the sustainability of its components. By managing its components, the resilience of a system will be assured.  Management of these components will require ‘metrics’, and these metrics will have a temporal dimension.  WLE researchers should aim at developing generic methodologies to determine metrics for management of various components of an ecosystem.  They will become WLE’s legacy.