Potential impacts for local resources & production

1. Potential impacts for local resources & production

2. Impacts on Agricultural Production • Decline in productivity due to increased drought and bushfire • Reduced runoff and quality of water supply (dams) • Production benefiting from warmer conditions (for initial warming) and higher carbon dioxide levels but vulnerable to reduced rainfall • Reduced quality of forage & grain protein levels due to elevated carbon dioxide level • Increase in extreme events (e.g. heat waves, drought, storms)

3. Enterprises & regions potentially at risk - • Those already stressed – economically or biophysically • Those at the edge of their climatic range or tolerance • Where large and long-term investments are being made

4. CO2 Impacts • Plants respond positively to higher CO2 by growing more efficiently for a given unit of sunlight and water • Greater effect on C3 species – cereals, cool season pastures, trees • However benefits will be moderated by: • Declining rainfall • Where temperature increases become too high (heat shock) • Increase in N use efficiency (C3) = reduced N in tissues • Implications for forage and grain quality • Legumes to benefit - response greater than grasses

5. Heat Impacts • Plant development & maturity will be accelerated • Greater exposure of stock and crops to heat-related stress and disease • Frosts • Warming may suggest less frosts – but not necessarily • Less soil moisture and more frequent high pressure systems are risk factors for frost. • Earlier flowering – may expose crops to a new / earlier window of frost risk

6. Water • Reduced runoff & water quality impacts • Non-linear relationship between rainfall & runoff • E.g. 10% reduction in Rainfall - could mean 30% reduction in Runoff • Seasonal impacts • Less autumn & winter rainfall – critical for runoff • Reduced winter flushing of salts from surface soils ? • More intense rainfall events + longer dry spells – water erosion? • Increased demand on water resources • Decreased supply • Greater ET for plants / water requirements for stock

7. Pest Plants & Animals • Expected southern migration of some pests (KI may be insulated to an extent?) • Potential increase in the distribution and abundance of some exotic weeds • Potential change in the competitive capacity of some weeds

8. Soils • Climate variability will impact on different soil types • Soils water holding capacity and texture • Need to understanding Plant Available Water. • Subsoil constraints • Comparison of soils

9. Field capacity Available Water Content Wilting Point Field capacity Available Water Content Wilting Point Soils - water availability & soil texture Data - pers. comm. David Maschmedt (DWLBC)

10. Soils & climate • In very dry seasons - sandy surface soils can be more reliable (than clays) • Sandy surface soils with a large PAWC (bucket size) are most resilient to a warming, drying climate • Higher clay content soils lose the most water via evaporation, and have higher thresholds before soil moisture is plant available (wilting point). • In good rainfall years larger PAWC (bucket size), of any soil type, will boost production • Clayey soil types can be of benefit for better retention of soil carbon (moisture, nutrients, structure) and lower wind erosion risk • In higher rainfall zones (KI), warming & drying could mean less waterlogging

11. Soils

12. Summing Up • Climate variability is expected to increase in impact • Impacts over the next 2 decades or so should be within farmer’s adaptive capacity • Costs of production may increase to offset pests, heat stress and feed availability • Longer term impacts are scary - mitigation is the key! • There is a danger of ‘mal-adaptation’ – e.g. in cases where short term trends (& investment) don’t reflect longer term climate trends. • Research & Extension agencies will aim to assist by providing best available, balanced information to support decisions