Effect of climate change on freshwater ecosystems

Possible risks and adaptation methods

Human-induced climate change will have a significant impact on freshwater ecosystems. Scientists foresee a decrease in wetter basins and an increase in drier basins in the future.

We have witnessed a fast climate change throughout New Zealand, Australia, and the Pacific highlands. This has altered the normal rainfall and temperature patterns and caused an increase in sea levels.

Anthropogenic (human-caused) climate change will cause damages that will lead to biodiversity loss. A good example is the Australian wetlands and rivers that have deteriorated due to water abstraction and regulation – leading to massive death of floodplain and wetland biotic lives.

It will affect freshwater ecosystem drivers: water temperature, water quality, and flow regime (or flow pattern). The rise of the sea level will significantly affect low-lying coastal wetlands, depending on the ecosystem or region. High temperature destroys animal habitats during low flow periods, therefore threatening the survival of species.

A combination of high temperature, flooding, and reduced rainfall (which leads to reduced flow) will highly affect aquatic lives. Macroinvertebrates, e.g., crayfish or stoneflies, will experience a big blow due to water-quality change, few dispersal routes, and other human-induced impacts that already exist.

Australia, being the driest continent, will specifically suffer the consequences of climate change. Its average temperature has been increasing since 1950, leading to harsh droughts, more fire risk, and reduced flooding. Scientists foresee an increase in extreme events such as flooding and drought in different parts of Australia.

The expected rise in sea level is a significant threat to coastal wetlands throughout Oceania. The composition and day-to-day lives of communities will change as animals disappear. As a result, new species will emerge. A good example is a change in migration and breeding of birds that is being witnessed.

Therefore, species or systems that depend on social-ecological systems will have to adapt or be eliminated. In this article, we will analyze how vulnerable freshwater ecosystems are and different measures that we can take to ease climate change problems throughout Oceania.

First, we look at the challenges for Macquarie Marshes and its history of environmental flow management to reduce regulation impacts. Second, we look at snowmelt rivers in Australia and the effects of climate change on them.

We will then compare Australian Alpine systems with snowmelt and glacial-fed streams in New Zealand. Then we will analyze the effects of sea-level rise on estuarine wetlands in coastal New Zealand and freshwater wetlands in the Northern Territory of Australia. 

Finally, we will look at the Pacific Islands (Melanesia, Micronesia, and small, developing island states of Polynesia), where sea level rise will significantly constrain adaptation opportunities.

Challenges for Macquarie Marshes

An example of the consequences of biotic systems regulation is the decade-long drought nicknamed the “Big Dry.” The Marshes experienced long-dry periods between 2001 and 2009 when the water sharing plan couldn’t regulate water use in the area. The program was eventually terminated.

As a result of reduced flooding, the waterbird population and wetland vegetation reduced. This issue forced the government and the commonwealth to allocate more funds to increase environmental water allocation for the Marshes by almost triple.

In the Murray-Darling Basin, runoff has reduced significantly due to a rise in the average seasonal temperature. This situation is projected to continue if no viable measures are taken, having already seen a 15% reduction in inflows with a 1% rise in average temperature.

In addition to the outcomes of climate change, e.g., reduced flooding, river regulation plays a big role in limiting the existence of many aquatic lives. Although many species in arid-zone wetlands are adapted to living in such fluctuating conditions, regulation has already exceeded the limit that they can tolerate for survival.

Decreased flooding due to reduced rainfall has had a significant impact on inland wetlands, which are already affected by river regulation. By 2070, the situation will most likely irreversibly alter the condition of the Macquarie Marshes.

These changes will affect wetlands that rely on targeted flow allocations. However, the existence of management means there is an enormous scope of strategies that can be used, e.g., dam reoperation, to counter these effects.

Australia’s snowmelt rivers

Snowmelt leads to the creation of leads that promote the diversity of water plants and animals. These changes could either be the growth, migration, etc., that are a result of the snowmelt. Globally, climate change will likely alter the timing, pattern, and volume of flows that result from snowmelt. A tiny area is affected by snow cover in Australia.

One significant regulation scheme implemented in the past was The Snowy Mountains Hydroelectric Scheme (SMHS), which was completed in the 1960s. It diverted 99% of flows from the southern flowing Snowy River to the west-flowing rivers, generated hydroelectricity, and provided water to the inland irrigation industry. This altered the existence and composition of aquatic life besides affecting the natural connectivity.

The SMHS is a huge network of large and small pools and diversion structures that enables water to be directed among reservoirs, passing through various hydropower stations before eventually flowing west via the Murray and Murrumbidgee valleys.

The Australian snowmelt pattern is rarely known due to the remote location of the ecology. The ability of Australia’s organisms and snowmelt streams to adapt to the climatic changes is blocked by few viable options for regulating water temperature and/or flow.

Flows coming from reservoirs can be created to resemble the natural flow to protect rivers from drought and regulation. However, regulation and human and animal invasion probably cause more harm than climate change.

Australian Alpine systems Vs. Snowmelt and glacial-fed streams in New Zealand.

Climate change affects freshwater lives in three major ways: Temperature increase, Rainfall changes, run-off, and its effects on sea-level rise.

Like in Australia, alpine and glacial rivers in New Zealand are affected by temperature rise, impacting cold-adapted species. However, projected water loss (by 2030) in arid wetlands is less than losses caused by water regulation in Australia.

There is no doubt that reducing greenhouse gas emissions will lessen the climate change impact on freshwater ecosystems in all these areas. Besides, more strict policies can be enacted to improve the situation – although the implementation of existing policies has been slow.

In New Zealand, water abundance and remoteness of melting glaciers may limit policy creation. For the Pacific Islands, lack of resources is the major block to creating and implementing policies to deal with climatic change.

Recommended adaptation measures to counter effects of climatic change on freshwater ecosystems

A critical adaptation method would be to apply policies used in aquatic ecosystems to other threats, e.g., river regulation. For land areas, increasing the protected area is essential – although this could be less successful for aquatic ecosystems unless freshwater inflows are protected.

For dry-area rivers, where enacted policies and climate change both increase drying, water buy-back, and environmental flows provide the primary adaptation to both regulation and human-forced climate change.

With the accelerating drying of freshwater ecosystems, connectivity may be lost between wetlands. Effects caused by a temperature increase in freshwater alpine ecosystems will be hard to handle. However, additional measures can be taken such as:

• Revegetation of riparian areas: It could reduce temperatures. However, it is challenging to implement in alpine areas.
• Translocation of important aquatic species: It is costly to implement and may affect the existing lives in the areas where the new species are introduced.
• Build levees to prevent salt intrusion where there are freshwater ecosystems: It is limited, and people will have to play a part to ensure that it is protected.

Besides this, there should be an effort to reduce other threats that affect the long-term conservation of aquatic life (e.g., pollution). Flushing flows can be used to maintain water quality. However, there needs to be more effort to prevent water pollution from urban, agricultural, industrial, mining waste, etc.

Conclusion

The impact of climate change on freshwater ecosystems worsens the current threats. As of now, the biggest problem is the accelerating temperature increase in alpine systems – which could cause the extinction of various cold-adapted species. In the inland river and wetland areas, climate change could cause more drying and severe outcomes, such as in the Murray-Darling Basin.

For the coastal areas, sea-level rise is the biggest threat as it could alter the composition of the existing species. Generally, all these results could stop or delay the progress towards rehabilitating wetlands.

At the global level, a reduction in carbon emissions should be prioritized. Some adaptations can also be implemented at the local level, such as levees, revegetation, and translocation.

Climatic change presents a major challenge for Oceania, given the limited options available to counter it. However, it has to be tackled to avoid suffering the long-term consequences on the existence of aquatic species that will occur with the increasing loss and reduction in operation in freshwater areas.