This page provides information about the impacts of the flooding on agriculture and bushland, including soils, production, supply, farm infrastructure and livelihoods.

What will be the effects on floodplains and bushland?

Large areas of bushland and floodplains have been inundated by floodwaters.

Native trees on floodplains are generally adapted to the natural cycle of floods and droughts that take place in Australia and they have lifecycles to match.

Floods can trigger dormant seeds to sprout. Similarly, insects and reptiles may come out of resting. Unfortunately floods can assist weed species during an extensive inundation, by carrying weeds on currents downstream into areas where they were not previously established.

Invasive animals may benefit in this way as well. Floods like this and worse have been happening in the Australian landscape long before human habitation.

How will plants and animals recover?

Floods like this and worse have been happening in the Australian landscape long before human habitation.

The short-term, broad ecosystem effects of floods, or droughts, have long shaped Australia’s biogeography.

Most native species have lifecycles that enable them to be adapted to survive the wet and dry. However, to enable animals and plants to recolonise landscapes they need refuges to retreat to during disturbances, for example, patches of vegetation and variations in topographies in the landscapes like hills.

We may expect to see shifts towards species and ecosystem types that can cope with higher rainfall and water disturbances because climate models are projecting that future extreme rainfall events are likely to be more intense (resulting in more severe flooding).

Farmers and graziers in the Darling Downs and Lockyer Valley regions in Queensland have battled recent droughts and now the floods. What effects will the recent flood events have on food production and what impact will this have on food supply for the South East Queensland and broader region?

It is not one story for all farmers, industries and regions.

The recent above average rainfall resulting in the widespread flooding across Queensland in particular, has severely impacted on production. Harvests have been delayed, crops and pastures have been submerged and killed, and produce spoilt.

But there are also many farmers who have benefited from the widespread good rainfall resulting in high yields and, with successful harvest, high profits.

For example, many of the grain crops suffering weather-damage have returned reasonable profits given good yields and high prices for feed grains. Horticultural production however has been significantly affected as South eastern Queensland. The Lockyer and Fassifern valleys, the eastern Darling Downs and the Toowoomba range are major production areas for a range of vegetable crops.

These include:

  • potatoes
  • brassicas (broccoli, cabbage, cauliflower and chinese cabbage)
  • onions
  • carrots
  • lettuce
  • sweet corn
  • celery.

Additionally, more than 60 per cent of Queensland's production of processing crops including sweet corn, beans, peas, beetroot, and carrots, come from these areas.

A wide range of other vegetable crops are also grown on a much smaller scale in southern Queensland and areas like Bundaberg.

How will the soil and moisture conditions affect the planting of the next (winter) crops?

There will be a wide range of impacts from the floods on future crops arising from soil and water changes.

In many cases the waters will recede and soil moisture levels will return to an acceptable level for farming operations.

Underground and surface irrigation sources will likely be replenished. There will be a wide range of impacts from the floods on future crops arising from soil and water changes.

In some areas there will be waterlogging that will delay or prevent summer or winter plantings and irrigation infrastructure will need to be repaired. While in other areas the increased water availability will allow a larger dryland cropping area to be farmed in the coming season.

Farms right across Queensland, Northern NSW, Victoria and Tasmania have lost massive amounts of topsoil - now settling in catchments downstream, what effect will this have on crop production in the future

The floods have removed significant amounts of topsoil over a large area of farming land. While some parts of the landscape have lost significant amounts of topsoil (both from the flood but also from the sheet erosion as rain fell on wet soils) other areas will benefit from the depositing of new topsoil.

However, the removal of topsoil is always a loss for agricultural productivity as topsoil is the part of the soil horizon with higher levels of organic matter and nutrients and generally better structure. Also where soil has been removed from actively cropped lands, the fertiliser that has been applied by the farmer has also been washed away.

These attributes are slow to replace (if ever) and ultimately reduce yield unless higher levels of inputs are applied, particularly in the short term.

Where soil is deposited, it is not necessarily a net benefit. It does not necessarily move to farmed areas but instead clogs streams, roads, fence-lines, buildings where the flow of water is slowed momentarily.

Erosion effects are different depending on the soil, the landscape form and the land management in place beforehand (for example, contour banks). The wide range of soil types across Queensland each have their own particular management problems; while the rains and flooding have caused massive erosion, landslips and loss of nutrient-rich topsoil, the effects will be site-specific. For example the rich red clay soils of the Toowoomba range are more acid with depth.

As the more neutral surface soil is lost through erosions, farmers may need to apply extra lime and nutrients before new crops can be planted. Winter farming systems across the black and grey clay soils of the Darling Downs region are based on building soil moisture from the summer rains; so there is some good news for this region come next season as farmers will have almost 100 per cent soil moisture to start their next plantings.

In addition, farmers relying on irrigation have replenished water supplies, in the case where dams and equipment have not been damaged. Successful farmers accurately match soil type, irrigation method and crop choice so decisions about next season’s crops and farm management practices will need to be reassessed due to the floods.

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