Climate change is often described as the change in the average weather over a long period of time, usually over a period of 30 years and can occur due to a combination of natural and human causes. The United Nations Framework Convention on Climate Change describes climate change as “…a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods.”
The majority of natural assets within the Corangamite region will be impacted by climate change. The region’s native vegetation, waterways, wetlands and soil are vulnerable to a hotter, drier climate. The region’s estuaries and coastal wetlands are vulnerable to sea level rise. It is expected that climate change will impact the region’s native vegetation through modifications to vegetation communities, such as loss of particular plant species and changes to community structure, as a result of higher temperature and lower rainfall, changes to natural fire and flooding regimes and climatic conditions favouring new and established weed species.
The Current Situation
The Corangamite region’s climate is classified as temperate Mediterranean. Summer and autumn are characterised by hot and dry conditions, and rainfall is dominant in winter and spring. The Otway Ranges experience the highest rainfall of the region, with 1500-1900mm annually, followed by the Western Uplands in the north with 1000-1100mm. The central Victorian Volcanic Plain experiences the lowest rainfall for the Corangamite region, of 500-600mm.
According to the latest Bureau of Meteorology regional weather and climate guide, in the 30 year period 1989-2018, the Corangamite region has experienced stable annual rainfall levels, that, while decreasing slightly over the time period, are within normal variability. The region has experienced 12 dry years over this time, with rainfall in the lowest 30%, and nine wet years, with rainfall in the highest 30%. Eight of the dry years accounted for occurred during the Millennium Drought.
Overall, rainfall is consistent and reliable throughout the years. It is at its most reliable during winter over the whole region, and the most reliable in the central south and south-west areas. Corangamite has exhibited a pattern of consistently drier autumns region-wide in last 30 years as compared with the previous 30. The Corangamite region’s ‘autumn break’, defined by greater than 25mm of rainfall over three days (around the beginning of the winter cropping season), has also been occurring in the central and northern parts of the region one or two months later than it did in the previous 30 year period. The number of hot days experienced by Corangamite in the last 30 years has been relatively stable. Ballarat has also been experiencing later and more frequent frosts.
The Victorian Government’s ‘State of the Environment’ Report, released in 2013, provides an overview of both the current condition of Victoria’s climate and trends based on past climatic data. It is important in planning for the future that we learn from the past and the report provides an excellent basis for this. The report states that:
- Average temperatures in Victoria have risen by approximately 0.8°C since the 1950s
- The severity, duration and frequency of heatwaves have increased.
- Between 1997 and 2009, Victoria experienced a record-breaking 13-year drought, the longest recorded period of rainfall deficits on record.
- Over the past two decades, there has been a large decline in autumn rainfall, a small decline in winter and spring rainfall, a small increase in summer rainfall, and reduced frequency of very wet years.
- Victoria experienced its highest summer rainfall on record in 2010–11. The record rainfall led to major flooding that affected a third of Victoria.
- Since 1993, Victoria’s sea level rise has been similar to global averages of 3 mm per year
- Annual sea-surface temperatures in south-eastern Australia increased at approximately four times the global average.
The future climate of the region is expected to be hotter and drier than today with a higher frequency of extreme weather events such as bushfires and floods. Victorian Climate Projections covering the Corangamite region forecast that both maximum and minimum temperatures will continue to increase. Extreme rainfall events are predicted on average to increase in intensity but remain highly variable in space and time. Rainfall is expected to continue to be very variable over time, but in the long term it is predicted to continue declining in winter and spring as well as autumn. By the 2030s, the Corangamite region is expected to experience an increase in daily maximum temperature of between 0.8-1.5°C (compared with the 1990s), and between 0.9-1.7°C for the Central Highlands, and 0.8-1.6°C for the Great South Coast.
Under a high emissions scenario, by 2090 the cities of Geelong and Ballarat will both have climates resembling inner New South Wales areas like present day Albury-Wodonga. This equates to an increase of annual average maximum temperature of over 3°C by 2090, and a drop in average annual rainfall of 70mm.
The Corangamite Natural Resource Plan for Climate Change identifies how climate change will impact on the region’s natural values:
Despite an overall trend of declining rainfall, more of the rain that does fall will be in increasingly extreme downpours. This is likely to lead to an increase in the incidence of flooding events, particularly in urbanised and small catchments. Extreme temperatures are likely to increase at a similar rate to average temperature. There will be a substantial increase in the temperature reached on hot days. There will be more hot days (greater than 35°C), and warm spells will last longer. The projected warmer and drier weather in the future is likely to increase the frequency and intensity of bushfires.
Projected sea level rise, temperature increase, reduction in rainfall and an increase in extreme natural events (i.e. flooding) are all expected to impact the ecology and dynamics of the region’s estuaries. Existing threats, such as acidification, changes to natural estuary openings and nutrient levels may also be exaggerated by the indirect impacts of climate change.
Higher temperatures and a drier climate will change the unique relationships that soil organisms have with plants. The loss of plants – within both natural and agricultural systems – will most likely increase the impact and extent of the soil threats listed above. Indirect impacts of climate change such as bushfires and flooding will also have direct erosion impacts.
The Barwon Climate Change Projections 2019 for part of the Corangamite CMA’s region, along with those for the Central Highlands and the Great South Coast cover the entirety of the region and provide a useful resource where results are shown for two plausible scenarios of future greenhouse gas emissions.
Although the impact of climate change on future temperature trends can be reasonably predicted, the impact of climate change on rainfall and river flow is far less certain. The following table shows recent predictions of percentage changes to average annual rainfall and streamflow for years 2040 and 2065 relative to a 1995 baseline. The predictions were calculated by DELWP using the results of global climate change models and rainfall/ runoff models.
The Corangamite Waterway Strategy 2014-2022 identifies some key issues for waterway management that include planning for climate change and managing extreme events. There will likely be a decrease in the number and area of permanent and seasonal wetlands and an increase in the number and area of intermittent wetlands. The most vulnerable wetlands will be those that are completely rainfall dependent.
Climate change will impact both the extent and quality of wetlands in the region through a reduction in the frequency and duration of rainfall events combined with an increase in the duration of drier periods, leading to the drying of shallow wetlands; drainage of existing freshwater wetlands due to changes in land management practices (i.e. from grazing to cropping); and changes to salinity levels due to higher evaporation rates. Wetlands that are dependent on groundwater will also be largely impacted by climate change though reduced inflows.
Those most vulnerable wetlands include freshwater meadows and marshes, as well as wetlands that are currently ephemeral in nature, both freshwater and saline. Iconic wetlands in this category include Lake Gherang, Lake Beeac and Lake Victoria, and many of the wetlands in the Western District Lakes landscape system. Wetlands that will be more resilient to climate change include those that are deeper and/or larger in size such as Lake Purrumbete.
With decreased rainfall and a warmer climate, there is an expectation that inflows into waterways will decrease which will have an impact on their functionality and environmental conditions. The scenario of more sporadic rainfall events of higher intensity could lead to more extreme events such as flooding. Lower rainfall will also have an effect on recharge into regional groundwater systems. The necessity for water supply for domestic, industrial and primary production may also have an impact on inflows into waterways.
The most vulnerable waterways in the region are those in the Otway Ranges, especially those flowing southwards into the Southern Ocean. These waterways have small, confined catchments, are unregulated, rely on high levels of rainfall and are relatively short in length. Reduced runoff into these rivers and streams will have a detrimental impact on these systems.
Some rivers and streams will be more resilient to climate change. These include reaches of the Gellibrand, Leigh, Moorabool and Barwon rivers and this high resilience can be attributed to these specific reaches being highly regulated flows and/or already highly degraded. As a result, there is limited scope for these reaches to be degraded further by climate change, mainly due to their already reduced flows.
The region’s estuaries are normally quite resilient to coastal processes such as tidal exchanges, shoreline recession and natural estuary openings. However, with sea levels projected to rise on average by 0.8–1.1 metres by 2100, combined with an increase in storm surge events and reduced inflows, climate change is expected to greatly impact all estuaries in the region
Rising sea levels will not only have an impact on the coastal environment but will also impact on the region’s estuaries. This will especially be the case where there are urban communities within the catchments and surrounds of these estuaries, especially the estuaries of the Curdies, Gellibrand, Aire and Anglesea rivers. It is also expected to have a major impact on the Barwon River estuary, especially in the upper reaches of the estuary into Lake Connewarre.
The South West Climate Change Portal provides the ability to look at the vulnerability and impact on a variety of natural resources to climate change, including rivers and streams, wetlands and estuaries.
It is expected that climate change will impact the region’s native vegetation through modifications to vegetation communities, such as loss of particular plant species and changes to community structure, as a result of higher temperatures and lower rainfall, changes to natural fire and flooding regimes and climatic conditions favouring new and established weed species.
Many species have evolved over thousands of years and may not have the ability to adapt to what will be a rapidly changing climate. A climate that is hotter and drier will lead to other indirect impacts such as changes to natural fire and flooding regimes. An increase in these events may have direct impacts on small, localised populations.
The South West Climate Change Portal provides the ability to look at the vulnerability and impact on a variety of natural resources to climate change, including native vegetation.
Vegetation communities that currently rely on wet climates with consistently high levels of rainfall are most vulnerable. Examples include the rainforests and wet forests of the Otway Ranges. Other vegetation communities vulnerable to climate change will be the riparian communities of the region, especially those found along the smaller tributaries that feed into the larger river systems. These vegetation communities are dependent on regular flooding or at least periods of inundation from heavy rainfall events.
Not all vegetation communities are highly vulnerable to climate change. Communities such as Coastal Scrubs, Salt Tolerant Shrublands and Heathy Woodlands are all quite resilient to hotter and drier conditions. Should such conditions eventuate, these communities are likely to have greater capacities to cope with change in both temperature and reduced rainfall because they occur naturally in such conditions today. However, climate change can have other – perhaps greater – impacts on native vegetation. One important driver is through changes to existing fire regimes, with more frequent and intense bushfires projected alongside smaller windows of opportunity for prescribed burning.
CSIRO has carried out modelling to map the distribution of Cool Temperate Rainforest under projected changes in the region’s climate. CSIRO’s modelling suggests that Cool Temperate Rainforest is likely to become even more restricted by 2050, and would virtually disappear from the region if the trend continued.
The habitat that is provided to a range of fauna species will be impacted by the scenarios outlined above. There are many vulnerable and endangered species within the region that will be further impacted by rising temperatures, less rainfall and change in habitat extent and type.
From Victorian Climate Projections 2019 and other research, we know over the long-term there will be even less rainfall, less run-off into our rivers and storages and more severe and prolonged droughts. The future scenarios of the region transitioning to a warmer climate with less rainfall will have an impact on how land is managed and the types of commodities produced. Climate change may provide opportunities that have not been possible in the past due to the climatic conditions. Agricultural productivity may increase or decrease under a changing climate, depending on where it is located e.g. from grazing to cropping. However, as a general rule, productivity will reduce as total rainfall declines.
Farmers may need to think more strategically about shifting some of their practices and sources of revenue to accommodate any medium and long term changes to the climate, or diversify their livelihoods to be less reliant on rainfall that experience and projections might indicate is becoming less reliable.
Climate change will have a direct impact on soil health and on its ability to support specific uses. Prolonged periods of higher temperatures and reduced moisture may lead to more areas being more susceptible to wind erosion. More intense rainfall events may also lead to areas of sheet, rill and gully erosion. Reduced vegetation cover due to climate change will also exacerbate these impacts. More frequent and intense fires may also change the structure and productivity of soils. An increase in dryness and lack of moisture will also impact organic carbon in soil.
The South West Climate Change Portal provides the ability to look at the vulnerability and impact on a variety of natural resources to climate change, including soils and land. It also outlines the adaptation processes that will need to be adopted in the short term to enable long term viability.
The Corangamite Soil Health Knowledgebase provides information from a range of sources that identify the impacts of climate change and how this impacts on the soils and agricultural landscapes of South West Victoria.
Coast and Marine
Climate change is now a focus of attention for coastal managers, and the first steps focus on changes to average states – average temperatures, mean sea level, wave action, etc. However, a key feature of climate change is not just “average” changes but increases in climatic variability.
For coastal environments, this variability may be reflected in changes to rates of opening and closing of estuaries, increased variability in river flows, and changes to frequency of storm waves and other severe weather events.
Sea level rise will also impact the region’s coastline through increasing inundation and erosion as well as direct impacts on coastal habitats and biodiversity, such as higher water temperatures on specific marine species and communities. Projected increases in storm surges will also directly impact the majority of the region’s coastal assets.
Changes in wind climate, especially in direction, can have significant impacts on the coast. A change in wind direction may result in a change in wave direction. A change in the strength and location of major storms in the Southern Ocean may result in a change in the level and direction of wave energy reaching the west coast of the Corangamite region. Sandy coastlines tend to align perpendicular to the average direction of incoming wave energy. If the average wave direction changes, there is a likelihood of changes to the alignment of sandy coasts with potential loss – or gain – of coastal land. An increase in wave energy may result in changes in beach slope and potential erosion of sandy beaches, as well as impacts on cliffy shorelines. This is of particular concern in areas such as Apollo Bay, Lorne, Anglesea and Ocean Grove.
More frequent and extreme storms will cause greater flooding of land and buildings on the coast, loss of and damage to private and public property and infrastructure, and beach, foreshore and cliff erosion.
Despite an overall trend of declining rainfall, more of the rain that does fall will be in increasingly extreme downpours. This is likely to lead to changed salinity, nutrient and sediment flows, changed estuaries, greater extremes of high and low fresh water input and reduced water clarity.
The South West Climate Change Portal provides the ability to look at the vulnerability and impact on a variety of natural resources to climate change, including coastal wetlands, which includes Swan Bay.
Climate change will impact the community in a number of ways. There will be the direct impact of the weather causing issues with higher temperatures; extreme weather events like storms, heatwaves and floods are predicted to become even more intense and destructive over the coming decades.
Important built assets, infrastructure and natural assets along the region’s expansive coastline may be at risk due to sea level rise, coastal erosion and inundation. Areas most vulnerable to inundation are generally beach fronts, low-lying wetlands and coastal reserve areas. Such inundation will have social as well as economic impacts on the community.
There are a number of resources available to support climate change decision making and adaptation. The South West Climate Change Portal provides general information about climate change, its impacts, how to plan for it, manage it and the different implementation approaches available. The Corangamite Natural Resource Plan for Climate Change provides support for the region to incorporate climate change mitigation and adaptation into NRM planning. It also aims to provide a blueprint for managing the region’s natural assets under a changing climate.
The Department of Environment, Land, Water and Planning has produced a range of climate change adaptation resources which can be found on its website. This site provides Place-based Climate Change Adaptation Resources including Guidance materials for place-based adaptation and regional climate change adaptation snapshot reports. It also includes Resources for Local Government that outline local government roles and responsibilities for adaptation under Victorian legislation, and a climate change data and information for local government factsheet. Also available at this site is information about communicating climate change and climate impact research as well as a range of other resources.
Victorian Climate Projections 2019 delivers local-scale projections of Victoria’s future climate. The Victorian Government has partnered with CSIRO to help Victorian communities prepare for climate change by providing authoritative and up-to-date information.
The Regional Weather and Climate Guides project is part of the Australian Government’s Drought Assistance Package. The project aims to improve the resilience of farming businesses by providing localised facts about the likelihood, severity and duration of key weather variables in regions across the country.
Embedding Climate Change
The Corangamite region’s natural assets, by definition, are adaptive as they have persisted through much climate change in the past. However, this adaptive capacity has now been compromised by environmental changes such as fragmentation, competition for water use and the introduction of foreign plants and animals. The best way we can help our natural assets adapt to climate change will be largely reflected in how we manage our catchments and landscapes into the future. It is important to note that the potential scale, timing and significance of a changing climate may mean our efforts to build the resilience of natural assets may not be enough. We may have to change or transform what we do and how we manage now, because the assets themselves may need to change dramatically.
The most appropriate method for embedding climate change into project development is through the use of an adaptation pathway approach.
Adaptation in NRM is an adjustment in response to actual or expected climatic change or its effects, which minimises detrimental impacts or encourages beneficial opportunities. For short-term adaptation to the impact of climate change consideration of climate variability, particularly extremes is important.
Adaptation is not a new concept in natural systems, however it is a fundamental requirement if systems are to exist under a changing climate. Adaptation in NRM is an adjustment in response to actual or expected climatic change or its effects, which minimises detrimental impacts or encourages beneficial opportunities.
Climate change is likely to have many and varied impacts on the region’s natural systems. There are three main types of adaptation and these will underpin the types of adaptation methods adopted in this plan, to ensure the region’s natural assets can adapt to an environment influenced by climate change.
- Resilience – the magnitude of change is small and predictable. Adaptation can occur in the form of incremental changes to current management of natural assets, e.g. fencing wetlands on the Victorian Volcanic Plain to protect them from stock and to allow them to build on their own adaptive methods to climate change.
- Transition – the magnitude of change is larger and less predictable. Change to current management of natural assets needs increased modification and new management measures, e.g. changing the amount of environmental flows in the Moorabool River to allow vulnerable fish species to adapt to projected lower stream flows.
- Transformation – change is large and the level of uncertainty requires fundamental changes to the management of natural assets, e.g. relocation of fish populations in small creeks to larger permanent waterways to ensure populations are maintained.
The potential scale and significance of a changing climate may mean our efforts to build the resilience of natural assets are not enough. We may have to change or transform what we do and how we manage, because the assets themselves may change dramatically. Equally, we won’t be able to just change from one thing to another, as we will need to ‘transition’ from one management action to another.
The Catchment Assessment Framework (CAF) was developed through the “Identifying low risk climate change mitigation and adaptation in catchment management while avoiding unintended consequences” project.
For aquatic ecosystems the framework is used to assess the climate change adaptation potential of nine natural resource management (NRM) actions in aquatic ecosystems:
- Environmental flows – releases of water for environmental purposes
- Environmental works and measures – structures designed to pool water on floodplains
- Thermal pollution control – devices to mitigate cold water pollution from dams
- Freshwater habitat connectivity – fish passage and removal of in-stream obstructions
- Restoration of riparian vegetation – fencing off riparian areas and revegetation with natives
- Conservation of more resilient landscapes – prioritising relatively undisturbed, more biodiverse areas
- Conservation of gaining reaches – areas where ground water flows into surface water
- Geomorphic restoration – re-snagging, removal of sand slugs and control of erosion
- Management of exotic species – removal or containment of non-native flora and fauna
Evidence has shown that ecological change in response to climate change is unavoidable, widespread and substantial. Our ability to manage biodiversity through these changes depends on understanding what the nature of the change might be and where the potential for future persistence of biodiversity may be greatest.
AdaptNRM has useful information about the implications of climate change on biodiversity and how to plan to address such change.
AdaptNRM is a national initiative that aims to support NRM groups in updating their NRM plans to include climate adaptation planning. There is useful information provided about what to expect with regard to weeds especially.
The Catchment Assessment Framework (CAF) was developed through the “Identifying low risk climate change mitigation and adaptation in catchment management while avoiding unintended consequences” project.
For terrestrial ecosystems the framework is used to assess the climate change adaptation potential of four natural resource management (NRM) actions in terrestrial ecosystems:
- habitat connectivity
- rehabilitation of refugia and habitats with favourable aspects
- rehabilitation of large habitats
- reduction of overgrazing.
Coast and Marine
CoastAdapt is an information delivery and decision support framework. It is for anyone with an interest in Australia’s coast, the risks it faces from climate change and sea-level rise, and what can be done to respond to those risks.
CoastAdapt contains information and guidance to help people from all walks of life understand climate change and the responses available to manage the impacts.
Blue Carbon Lab sits within the School of Life and Environmental Sciences at Deakin University. Their mission is “to offer innovative research solutions aiding to help mitigate climate change and enhance our blue economy, while simultaneously supporting aquatic biodiversity, economic growth, capacity building, and community wellbeing”. This site provides information about research and publications relating to a range of coastal adaptation approaches and the opportunities for carbon sequestration within the aquatic and marine environments.
The Climate Resilient Communities of the Barwon South West project is a collaboration between 10 Councils in the Barwon South West region and a range of partners, including Catchment Management Authorities and water authorities.
The project began in 2012 with the aim of helping communities throughout the region to understand what risks and opportunities might be presented by future extreme weather events. It has sought to build municipal preparedness to extreme climate events through a wide range of planning and embedding projects.