How can environmental research and monitoring help manage productivity, biodiversity and ecosystem services for a growing population?
Producing sufficient food, feed, fuel and fibre has been a perennial challenge for landholders down through the ages. Constraints on productivity include the need for suitable arable land, fertile soils, sufficient water through rain or irrigation and adequate management of pests and diseases. With the world’s population having now grown to seven billion, we need to manage such constraints more effectively than ever before.
Importantly, we are also now realising that addressing production constraints must be done in a way that is sustainable: we cannot pursue short-term gains whilst neglecting longer-term sustainability goals which include protecting biodiversity, climate stability and freshwater resources.
Thus, in addition to the urgent need of supplying adequate agronomic inputs to provide for a growing population, there is a heightened priority to protect ecosystem services: the result is greatly intensified competition for land uses and resources.
Current concerns with the global carbon cycle
A major element to protecting ecosystem services is balancing natural biogeochemical cycles in order to prevent major disruptions to how these processes operate in our biosphere. These include the water cycle and the carbon cycle and in the latter case there is much present concern on how human activities have disturbed rates of carbon flux between the atmosphere and terrestrial and aquatic ecosystems. Modern societies are heavily reliant on fossil fuels which originate from organic matter accumulated many millennia previously by the capture of atmospheric CO2 through the photosynthetic activity of primary producers. When fossil fuels are burned in large quantities, CO2 emissions exceed the rate of CO2 fixation by contemporary primary producers: the result is rising atmospheric CO2 concentrations with concerns as to how this may affect the temperature regime of our planet.
There is now pressure to reduce the burning of fossil fuels in favour of ‘clean’ or renewable energy sources, and also to offset remaining emissions through sequestration programs. In both cases woody and herbaceous crops play a major role. In the first case, ‘biofuels’ are considered a renewable and sustainable source of energy since the production and consumption of these fuels, and therefore the capture and release of CO2, occurs concurrently in a tight cycle. Important biofuels include fermentable crops such as sugar cane and corn, or crops which produce combustible oils such as Jatropha, sunflower and oil mallee. In the second case, where sequestration programs are being implemented to capture excess atmospheric CO2, there are a number of strategies being pursued including tree planting to lock up CO2 in woody biomass or changes to tillage and other agronomic practices to store more organic carbon in soils.
What are the impact of new crops and land management practices?
Whilst many new cropping systems and agronomic practices are being put forward to address issues related to the CO2 emissions it is critical to realise that the carbon cycle cannot be view in isolation from other biogeochemical cycles and ecosystem processes. Clearly, in order to grow crops to reduce fossil fuel use or to capture CO2 emissions, other resources are needed: land, nutrients, water, labour, pesticides, etc. It is instructive to keep the basic biology of primary producers in mind when trying to understand how various biogeochemical processes are fundamentally linked. Firstly, the photosynthetic machinery inside every plant cell that captures carbon must be first built from important nutrients such as nitrogen, phosphorus, potassium, magnesium, etc. Secondly, for terrestrial plants, atmospheric CO2 can only be captured if plant surfaces are permeable to gases: this occurs when the pores in plant leaves (stomata) open and a consequence of being able to absorb CO2 is that water vapour is invariably lost.
Indeed, a far greater amount of water is forfeited than CO2 captured every time leaf stomata open. Thus if we want to capture carbon to produce biomass (to burn as fuel or keep as a carbon sink) we must be prepared to pay a price in water, nutrients and arable land. If cropping systems are implemented at a large scale without due consideration of the wider impacts there could be drastic consequences including drying of streams, changes to groundwater and groundwater dependent ecosystems, salinisation, acidification or other problems.
How can we evaluate the costs, benefits and unforseen consequences of new cropping systems?
Cropping systems 1) use resources as inputs, 2) transform and sequester resources during growth processes, and 3) release resources as outputs (e.g. runoff, respiration, etc.). To understand a cropping system it thus makes sense to be able to evaluate the resource inputs, transformations and outputs.
This can be done through direct measurements and the results of these measurements further extended into predictive tools through modelling exercises. Since we are dealing with flows and transformations of resources, effective measurement means we have to ‘stand in the flow’ with our tools so to speak in order to capture the information we need.
For example xylem sap flows can be measured using implanted thermometric devices (sap flow meters) which can directly measure amounts and patterns of water use in real-time. They do this by releasing a small pulse of heat into the flowing sap stream and then recording its movement using small temperature needles.
Other techniques such as dendrometers can provide real time information on plant growth rate as well as give insights into the tissue pressures found in xylem and phloem as water and sugars move within the plant.
Radial dendrometers employ twin high resolution (micron) displacement transducers fitted so as to measure the changes in bark and wood radius of a woody plant. These measurements are sensitive enough to show small changes in plant diameter as plants shrink or swell slightly in response to changing water status in response to changing cloud cover. In addition to such fine detail they of course show seasonal and annual growth trends with ease.
When combined with basic meteorological and soil moisture sensors, we can build a ‘whole-system’ picture which relates plant growth and water use to environmental conditions.
Armed with such key information, a range of important questions can begin to be addressed, for example 1) which species exhibit favourable water use efficiencies (most carbon capture per unit water use), 2) which species are best suited to which soil conditions and landscape positions, 3) which management practices show best yield responses, etc.
Importantly, such data also provide information on the bigger picture as what impacts plant growth is having on the wider landscape – e.g. groundwater dynamics, regional water balance, etc.
Thus a suite of techniques that can simultaneously monitor resource use and the consequences for plant growth and the wider environment is critical to putting a cropping system into context both in economic and environmental terms.
ICT International prides itself on delivering a comprehensive toolkit of complimentary techniques, supported by state-of-the-art and user friendly plug and play electronics systems to ensure that data is captured in high resolution and delivered reliably to the end-users’ desktop PC.