Drought in the Murray River doesn’t just affect the river itself – it also affects the ecosystems that live in the ocean beyond.
In a study published in Marine and Freshwater Research today, we found that the very low flows in the river over the past decade reduced the abundance of microscopic marine plants called phytoplankton, which are ultimately the base of all marine food webs.
This shows that the health of the Murray River has a much bigger influence on the marine environment than we previously realised. With climate change poised to make droughts more frequent and severe in the river, it will be crucial to monitor the health not just of freshwater species, but of the local marine ones too.
Read more: Is the Murray-Darling Basin Plan broken?
Phytoplankton depend on nutrients, which are often delivered to the ocean by rivers. In turn, these tiny plants are a source of food for almost all marine ecosystems. Worldwide, they are responsible for half the production of organic matter on the planet.
In South Australia, a dry period dubbed the Millennium Drought (2001 to 2010) and overallocation of water resources (primarily for agriculture) meant that very little water was delivered from the Murray Mouth to the coastal ocean. Between 2007 and 2010, no water was discharged at all. The water in the river’s lower reaches became much saltier and cloudier.
We used historical flow records and satellite imagery, taken between early 2002 and late 2016, to figure out how much phytoplankton and other organic matter were in the coastal ocean each month. We broke up the area into incremental zones, venturing up to 130km from the river mouth.
We found that during and after high-flow events, Murray River discharge resulted in a huge increase in phytoplankton concentrations – as far as 60km beyond the river’s mouth. Surprisingly, before our research it wasn’t known that the river played such an important role in stimulating phytoplankton growth over such a large area.
Armed with an understanding of how river flows influenced phytoplankton growth, we used historic flow records to estimate phytoplankton concentrations back to 1962. Our results showed that large flows used to occur more often and in greater volumes, and consequently that phytoplankton populations would have gone through more frequent and larger booms.
This in turn would have benefited all of the species that ultimately depend on phytoplankton for food, either directly or indirectly. This food web encompasses almost the whole marine ecosystem.
The past affects the future
Water resource management has greatly altered the volume and timing of freshwater discharges from the Murray. The ocean beyond the Murray mouth now receives small and infrequent deliveries of freshwater.
Rainfall and streamflow are decreasing in this already variable region, while temperatures are rising. This means that South Australia is likely to experience more severe and more frequent droughts, which will cause flows from the Murray mouth to decline still further, ultimately reducing phytoplankton abundance.
Previous research had already established the links between river outflows, phytoplankton and health of marine environments and species. But as far as we can tell, no other research has looked at exactly how extended periods of no or low river outflows affect marine ecosystems. This makes it difficult to predict how these systems will respond to climate change.
We believe that reduced Murray River outflows and reduced phytoplankton concentrations would likely have also placed strain on local mulloway fish and Goolwa cockle populations. Juvenile mulloway use river outflows as habitat and environmental cues, and cockles feed on organic material in the water.
This is why it is so important that the management of the Murray River doesn’t just stop at the river’s mouth, but continues into the ocean beyond. Current plans are focused on restoring flows to support the riparian and wetland ecosystems of the Murray as well as the Lower Lakes and Coorong.
But there has been little recognition of the role of river outflows on the marine environment – let alone in management. Although we might not always think about it, the marine environment is really the end of the river system, and part of a larger global cycle. It would therefore be beneficial if plans extend to monitor the marine ecosystem’s response, both at broad and fine scales, to varying flow events.
It would seem the time is past ripe to call for greater research and consideration on this matter, so that we don’t do further damage to what is actually still a part of the Murray River system, and can improve measures to protect the marine environment.
Many observers of China’s escalating global program of foreign investment and infrastructure development are crossing their fingers and hoping for the best. In an ideal world, China’s unbridled ambitions will improve economic growth, food security and social development in many poor nations, as well as enriching itself.
Such hopes are certainly timely, given the isolationism of the US Trump
administration, which has created an international leadership vacuum that China is eager to fill.
But a close look reveals that China’s international agenda is far more exploitative than many realise, especially for the global environment. And the Chinese leadership’s claims to be embracing “green development” are in many cases more propaganda than fact.
To help steer through the maze, I provide here a snapshot of China’s present environmental impacts. Are China’s assertions reasoned and defensible, or something else altogether?
For a start, China is overwhelmingly the world’s biggest consumer of illegally poached wildlife and wildlife products. From rhino horn, to pangolins, to shark fins, to a menagerie of wild bird species, Chinese consumption drives much of the global trade in wildlife exploitation and smuggling.
Over the past 15 years, China’s rapacious appetite for ivory has largely driven a global collapse of elephant populations. In response to growing international criticism, China promised to shut down its domestic ivory trade by the end of 2017.
But even before China’s ban has taken full force, a black market for ivory is developing in neighbouring Laos. There, Chinese entrepreneurs are churning out great quantities of carved ivory products, specifically designed for Chinese tastes and openly sold to Chinese visitors.
More damaging still are China’s plans for infrastructure expansion that will irreparably degrade much of the natural world.
China’s One Belt One Road initiative alone will carve massive arrays of new roads, railroads, ports, and extractive industries such as mining, logging, and oil and gas projects into at least 70 nations across Asia, Europe, and Africa.
Chinese President Xi Jinping promises that the Belt and Road initiative will be “green, low-carbon, circular and sustainable”, but such a claim is profoundly divorced from reality.
As my colleagues and I recently argued in Science and Current Biology, the modern infrastructure tsunami that is largely being driven by China will open a Pandora’s box of environmental crises, including large-scale deforestation, habitat fragmentation, wildlife poaching, water pollution and greenhouse gas emissions.
China’s pursuit of natural resources is also escalating across Latin America. In the Amazon, for example, big mining projects – many of which are feeding Chinese industries – don’t just cause serious local degradation, but also promote widespread deforestation from the networks of roads bulldozed into remote areas to access the mines.
Overall, China is the most aggressive consumer of minerals on the planet, and the biggest driver of tropical deforestation.
Beyond this, China is pushing to build a 5,000km railroad across South America, to make it cheaper for China to import timber, minerals, soy and other natural resources from ports along South America’s Pacific coast. If it proceeds, the number of critical ecosystems that would be impacted by this project is staggering.
A World Bank study of more than 3,000 overseas projects funded or operated by China revealed how it often treats poor nations as “pollution havens” – transferring its own environmental degradation to developing nations that are desperate for foreign investment.
Finally, much has been made of the fact that China is beginning to temper its appetite for domestic fossil-fuelled energy. It is now a leading investor in solar and wind energy, and recently delayed construction of more than 150 coal-fired electricity plants in China.
These are unquestionably pluses, but they need to be seen in their broad context. In terms of greenhouse-gas emissions, China has exploded past every other nation. It now produces more than twice the carbon emissions of the United States, the second-biggest polluter, following the greatest building spree of coal, nuclear, and large-scale hydro projects in human history.
Despite its new post-Trump role as the world’s de facto climate leader, China’s overall agenda could scarcely be described as green.
Some would say it’s unfair to criticise China like this. They would argue that China is merely following a well-trodden path of exploitative development previously forged by other nations and colonial powers.
But China is not the same as any other nation. The astounding growth and size of its economy, its dangerously single-minded vision for exploiting natural resources and land internationally, its intolerance of internal and external criticism, and its increasingly closed media and official myopia all combine to make it unique.
President Xi admits that many Chinese corporations, investors and lenders operating overseas have often acted aggressively and even illegally overseas. But he says his government is powerless to do much about it. The most notable government response to date is a series of “green papers” containing guidelines that sound good in theory but are almost universally ignored by Chinese interests.
Are Xi’s assertions of powerlessness believable? He increasingly rules China with an iron hand. Is it really impossible for China to guide and control its overseas industries, or are they simply so profitable that the government doesn’t want to?
Of course, China’s huge international ambitions will have some positive effects, and could even be economically transformative for certain nations. But many other elements will benefit China while profoundly damaging our planet.