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Good planning maintains biodiversity on farms

Farming and native biodiversity are not mutually exclusive. Landscape planning is one approach that lets the two land uses coexist, explains Sue McIntyre.

The 20th century saw a wealth of innovations in agriculture that allowed increased food and fibre production, and with it prosperity. But our society is now realising that the fertilisers, pesticides, machinery and non-native pastures that brought these benefits have produced a corresponding problem for native biodiversity. And that raises the question: What are we going to do about minimising environmental harm? Indeed, what circumstances allow the twin objectives of productivity for human uses and nature conservation to be met?

Biodiversity relies on sufficient suitable habitat for native plants and animals to feed, breed, shelter and move around. While intensive agriculture impacts on the availability of habitat, landscape planning is an approach that can enable farming and native biodiversity to coexist.

Landscape planning focuses on both the amount and the arrangement of native habitat across a landscape. The aim is to connect habitat, allowing organisms to move between different areas to meet the essentials of survival. Without these 'connected landscapes' many animals (like the female bird seeking a mate below) and many more plants are unable to move from small fragments of bush across extensive cleared areas.

The extent to which a habitat is connected, allowing the native animals and plants to survive and thrive, depends on three factors:

the amount of habitat,

whether the habitat is arranged in isolated fragments or one continuous strip, and

the extent to which adjoining land use interferes with the way in which species can use the habitat.

Landscapes are finite, so habitat connectivity will impact on the use of the availability of farm land for production. The question for farm and landscape planning is: 'How much intensive production can take place without excluding most native species from the landscape?'

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How much native habitat is enough?

Generally speaking, if intensive land use that largely excludes native biodiversity (crops, plantations, fertilised pastures) covers less than one-third of the landscape, it is unlikely to lead to the disappearance of native plants and animals. The habitat on the remaining two-thirds of the landscape allows species to move around freely, regardless of how it is arranged.

But when intensive land use covers more than one-third of the landscape, the arrangement of the remaining habitat becomes critical for connectivity. Connecting a smaller stretch of habitat in a single strip would give a species the opportunity to travel a long distance, but this form of connectivity may not be adequate for the wellbeing of the species. For example, a narrow roadside strip of reserve with a minimal shrub layer passing through cropland may provide poor protection to small birds travelling along it from predatory birds that thrive in open areas.

Regardless of how well connected habitat is, the activities in the remaining landscape are important in determining exactly which species thrive and which do not. Crops and fertilised pastures can be poor neighbours to bushland or creeks if excess nutrients wash into these areas and encourage natives to be replaced by weeds. Even everyday decisions like the location of a shed can impact on native species. Conversely, planting trees adjacent to crops can encourage some native birds to forage on the fertile areas and native insects to assist pollination, while also providing a safe retreat and breeding sites. But if the feeding birds are damaging the crop, their presence might be viewed differently by producers.

It's clearly a question of trade-offs, and based on a review of the evidence, scientists have developed suggestions for the relative balance of different land uses across a landscape, known as the 10:20:40:30 guidelines.

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10:20:40:30 — the key to a balanced landscape

A balanced range of land use intensities can provide a variety of landscape elements able to support the majority of local native species together with a range of human activities. The 10:20:40:30 landscape planning guidelines suggest a minimum of 10 per cent native vegetation managed for conservation, and less than thirty per cent of the landscape to be used for high intensity production. The remaining land is used for moderate intensity production, and native vegetation for production (eg grazing on perennials, native forestry).

The habitat connectivity resulting from this balance of different land use intensities is outlined in the following table.

On the ground, these guidelines translate to something like the idealised map of a grassy woodland property below. The property has been developed for maximum intensive land use (30 per cent) and grazing (90 per cent) but within the developmental limits for biodiversity conservation and provision of ecosystem services described in the table above. Land uses have been located so as to maximise connectivity for native plants and animals.

While biodiversity conservation in agricultural landscapes has been strongly driven by the voluntary actions of landholders, not all landholders are inclined or able to implement these landscape planning guidelines.

In recognition of this, several strategies have been developed by governments to encourage voluntary biodiversity conservation on private land. Continuing progress will rely on technical support, policies, legislative arrangements and financial assistance.

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It comes down to us

Native species will survive best in farming and forestry landscapes when activities that continue to create positive long-term attitudes to biodiversity conservation are designed and implemented.

Many serious decisions affecting native plants and animals are everyday actions which superficially appear to have little consequence for conservation: the location of a shed, the decision to fertilise a lawn or paddock, the choice of plants selected from the nursery, or where heavy machinery is parked by the road. As personal awareness grows, it will influence the multitude of these small decisions, and may motivate us to tread more lightly on the landscape.

About the author: Dr Sue McIntyre Dr Sue McIntyre is a research fellow with CSIRO Land and Water. This is an edited extract from a chapter she contributed to CSIRO's free e-book Biodiversity: Science and Solutions for Australia.



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