Adapting to Climate Change on Farms using Natural Sequence Farming Methods
Natural Sequence Farming (NSF) was developed by an Aussie - Peter Andrews, who is a third generation farmer and horse breeder. Over 60 years of farming he realised that clearing of the riparian (shoreline) vegetation and erosion of the stream bed has meant that the stream flows have become 'flashy' and have lost the ability to store water.
Streams have lost contact with the water tables and wetlands in riparian zone and the floodplain and so have lost the natural storage that acted to insulate the stream from droughts.
Restoring the connections and replenishing the water reservoirs in the pools, watertable, riparian areas and the floodplain margins helps to adapt the watershed to climate change. The restoration of the vegetation in the riparian and floodplain areas also helps to drought proof the stream and increases its resilience.
Peter Andrews claims that these changes in the landscape make the dry spells turn into drought conditions faster and more frequently than they should.
Clearing of the flood plain, over grazing of the banks and loss of vegetation following European settlement, has caused the stream to erode its bed.
Runoff rates have been increased significantly increasing stream velocities and this had led to more incision and erosion of the banks.
The lower streambeds have meant that the water tables on the floodplains have drained and are no longer replenished by moderate to high flows in the stream.
The problem has been made worse by the removal of logs and woody debris from the stream as a flood control measure.
The natural stream with its slower velocity and delayed runoff would not have flooded as frequently and would not have caused as much of a problem.
The changes also lead to a loss in biodiversity and huge costs associated with the need for more dams and other water storages and supplies and for controlling erosion.
A large number of properties have been transformed by applying these NSF principles. This has restored the health of streambeds, riparian zones and floodplains and has meant that the stream holds water in its pools for much longer periods. It has added benefits in increasing the productivity of the riparian areas and floodplains for grazing purposes. When the stream is reconnected with the water tables and wetlands the grasses and herbs return and become much more vigorous.
The restoration is accomplished by a series of physical interventions in the landscape aimed at slowing the rate of water flow and increasing water retention in pools and temporary storages especially after rain events.
It is wrong to assume that the method is aimed at restoring the landscape back to exactly how it was prior to European settlement. This cannot be done because the watershed has been cleared and modified. Rather NSF aims to restored the way the natural system worked in its pristine condition particularly in terms of the stream and its role in the landscape. The need for bulldozers and other heavy machinery is controversial.
The Proof is in the Pudding - The land shown on the right of the photograph was farmed using NSF and that on the left was not.
The increased vegetation cover and greenness is only part of the success story – the topsoil on the right is rich and deep and very productive.
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The method is particularly applicable to lowland streams that have floodplains, rather than the upland rocky bed streams towards the head of the watershed. It is also applicable to lowland stream that natural had a chain of ponds or a sequence of ponds in a meandering stream.
What are Natural Sequences?
This refers to is the natural movement of water, nutrients, sediments down the drainage lines and valley sides via the water cycle, seed dispersal, vegetation, and soil processes, continuously building, restoring and sustaining the fertility of the landscape. It also refers to the flow of water and sediments down the drainage lines to the cycling to and from the stream onto the riparian areas and floodplain and the water table. The natural sequence refers to the way the natural stream functions and operates and includes the biological processes as well. NSF management aim to restore and maintain the connection between the various natural functions which allows for quick exchange and conversion of nutrients within ecosystems on properties and exchange of water between the stream, water table, riparian zone and floodplain.
Design
The first step is the design - to identify where and how the interventions can be applied. This is the crucial first stage and is the most difficult. It tales a lot of understanding and experience to get it right.
Interventions
The method involves a series of interventions to restore the natural functioning of the processes through restoring the connections between the stream and the riparian zone, water table and floodplain. The interventions are designed to slow the flow down and to increase the water level in the channel at a series of 'leaky weirs' to recreate a chain of ponds The ‘leaky weir’ are constructed of rocks, logs, branches, gravel and sediment. Various trees, reeds, shrubs and grass are planted on and around the weirs to stabilise them. The aim is to mimic the original natural impediments to flows that slowed the stream down and allowed some of the water to disperse. These weir raise the water level and replenish the water table and water the edges of the riparian zone. This allows reeds and grasses to be reestablished as meadows beside the stream.
To recreate or enhance the chain of ponds system and re-water the floodplain areas, NSF designs includes a series of small minor diversion channels to spread some water onto the floodplain areas. These channels divert water out across the floodplain refilling ponds, water tables and wetlands. Any excess water flows back to the main channel through surface flows and drainage from the watertables. These channels work when there are moderate or peak flows using water diverted by the leaky weirs.
The water stores in the groundwater and on the floodplain buffers the stream against drought and keeps the channel wet for longer periods. This helps to maintain water in the channel and freshes pass straight through. There is much less need to wet the dry bed of the channel before the water can pass downstream.
NSF designs have been are used on a wide variety sites including eroded dry gullies, upland fast-flowing water courses, stream with eroded banks and incised channels, wetlands, broadacre cropping areas, wide floodplain valleys and salt encrusted degraded lands. Many farmers are attracted by the more sustained water levels in the stream for watering stock and the lush growth of grass along the margins of the stream. Others are attracted by the drought-proofing and increased biodiversity of flora and fauna along the stream. The system also offers benefits for carbon farming as it increases the amount of carbon stored in the vegetation and soils. Finally the system has many benefits for reducing erosion of banks and stops the stream incising into the bed. The extra water tends to provide for sustainable vegetation along the banks on the floodplains.
NSF Benefits for Grazing
The improved groundcover and restored vegetation along the banks provides many benefits for grazing with perennial grazing areas maintained on the floodplains and in the riparian zones. Under NSF, livestock are considered as major contributors to land management, including for providing improvements in soil fertility and weed control.
NSF Benefits for Agriculture
Horticulture can be focused into areas off the floodplain areas hich can be devoted to grazing, with various transfers of fertility and water within the NSF system. Irrigation is best-sited on valley floors although the recharging of the floodplain may mean less irrigation is needed. Some NSF systems are designed to divert water through the contours in the landscape and increase the amount of water in the soil profile.
Sustainable Landscape Outcomes under Natural Sequence Farming
Stream water is carried onto the flood plain, which in heavily eroded and incised channel may be rarely flooded
- The wetlands and stream side meadows are regenerated as sustainable high value ecosystems promoting biodiversity
- Farm managers change their attitudes to local flood inundation and see it as a beneficial part of the natural sequence.
- Floodplains and water tables are maintained by being recharged from the stream
- Erosion is controlled and the system promotes the build up of sediments in the stream reversing the erosion process that have destroyed the banks and led to incision of the beds.
- Polluted stream water is filtered and purified as it moves through the chain of ponds, wetlands, lush floodplain meadows, and groundwater.
- Whole-of-farm ground cover is increased and the perennial vegetation controls weeds. Biodiversity is maintained at a high level with the diversity of habitats created by the natural vegetation and aquatic sequences.
Criticisms and Opponents
There are critics and opponents of Natural Sequence Farming which centre on:
- Many farmers have worked for years to 'clean' their stream channels to promote the flow of water. After Natural Sequence Farming streams appear to be clogged with 'leaky weirs', rocks, debris, reeds and other vegetation. Opponents are concerned that this could cause 'break aways' where the stream starts to erode and move to new channels and to braiding.
- The neighbours downstream may be concerned that NSF will reduce downstream flows as it is designed to divert and store flows. The advocates of NSF have argued that this reduction in flow will be minor because NSF keeps the stream bed wet and the water storages topped-up. Moderate and high flows will be unaffected.This also means that flows are not consumed by wetting the stream bed and filling up these storages. They also argue that NSF simply restores the natural flow regime.
- One major criticism is that NSF has advocated the preliminary use of weeds such as willows to stabilise the banks and control erosion. Advocates of NSF claim that many weeds are pioneer species and are much better as stop-gap measures. The weeds can be controlled once the native species have regenerated. In many cases this replacement occurs naturally. The use of weeds and non-endemic species as pioneers has been very successful for regenerating rainforest margins along streams. The slower growing native species eventually shade out the initial weed plantings.
Conclusion
Preliminary trials and ongoing research demonstrates that NSF offers a cost-effective and 'working with nature' approach for dealing with modern farming problems and challenges – repairing degraded streams and watershed and the management of landscapes that are prone to leach salts into water courses. It also offers to restore the natural connections between the stream and its riparian zone and floodplains and to restore fertility and increase productivity and biodiversity. It offers hope for addressing unsustainable cropping and grazing practices.
NSF has the potential to offer significant economic, environmental and social returns to landholders and communities. It also has major benefits in adapting to Climate Change and reducing its impact.