A new report has warned that even if global warming is held at 1.5℃, we will still lose a third of the glaciers in the Hindu Kush-Himalaya (HKH) region. What does that mean for rivers that flow down these mountains, and the people who depend on them?
The HKH region is home to the tallest mountains on Earth, and also to the source of rivers that sustain close to 2 billion people. These rivers supply agriculture with water and with sediments that fertilise soils in valleys and the floodplain.
Some of these rivers are hugely culturally significant. The Ganges (or Ganga), for instance, which flows for more than 2,525km from the western Himalayas into the Bay of Bengal, is personified in Hinduism as the goddess Gaṅgā.
Before we get to the effect of melting glaciers on Himalayan rivers, we need to understand where they get their water.
For much of Himalayas, rain falls mostly during the monsoon active between June and September. The monsoon brings heavy rain and often causes devastating floods, such as in northern India in 2013, which forced the evacuation of more than 110,000 people.
But the summer monsoon is not the only culprit for devastating floods. Landslides can dam the river, and when this dam bursts it can cause dramatic, unpredictable flooding. Some of those events have been linked to folk stories of floods in many cultures around the world. In the Himalayas, a study tracking the 1,000-year history of large floods showed that heavy rainfall and landslide-dam burst are the main causes.
When they melt, glaciers can also create natural dams, which can then burst and send floods down the valley. In this way, the newly forecast melting poses an acute threat.
The potential problem is worsened still further by the Intergovernmental Panel on Climate Change’s prediction that the frequency of extreme rainfall events will also increase.
What will happen to Himalayan rivers when the taps are turned to high in this way? To answer this, we need to look into the past.
For tens of thousands of years, rivers have polished rocks and laid down sediments in the lower valleys of the mountain range. These sediments and rocks tell us the story of how the river behaves when the tap opens or closes.
Some experts propose that intense rain tends to trigger landslides, choking the river with sediments which are then dumped in the valleys. Others suggest that the supply of sediments to the river generally doesn’t change much even in extreme rainfall events, and that the main effect of the extra flow is that the river erodes further into its bed.
The most recent work supports the latter theory. It found that 25,000-35,000 years ago, when the monsoon was much weaker than today, sediments were filling up Himalayan valleys. But more recently (3,000-6,000 years ago), rock surfaces were exposed during a period of strong monsoon, illustrating how the river carved into its bed in response to higher rainfall.
So what does the past tell us about the future of Himalayan rivers? More frequent extreme rainfall events mean more floods, of course. But a stronger monsoon also means rivers will cut deeper into their beds, instead of fertilising Himalayan valleys and the Indo-Gangetic plain with sediments.
What about glaciers melting? For as long as there are glaciers, this will increase the amount of meltwater in the rivers each spring (until 2060, according the report, after which there won’t be any meltwater to talk about). So this too will contribute to rivers carving into their beds instead of distributing sediments. It will also increase the risk of flooding from outburst of glacial lake dams.
So what is at stake? The melting glaciers? No. Given thousands or millions of years, it seems likely that they will one day return. But on a more meaningful human timescale, what is really at stake is us – our own survival. Global warming is reducing our resources, and making life more perilous along the way. The rivers of the Himalayas are just one more example.
On Friday, Chief Judge Brian Preston of the New South Wales Land and Environment Court handed down a landmark judgement confirming a decision to refuse a new open-cut coal mine near Gloucester in the Hunter Valley. The proposed Rocky Hill mine’s contribution to climate change was one of the key reasons cited for refusing the application.
Defeating a mining proposal on climate grounds involves clearing several high hurdles. Generally speaking, the court must be convinced not only that the proposed mine would contribute to climate change, but also that this issue is relevant under the applicable law.
To do this, a litigant needs to convince a court of a few key things, which include that:
the proponent is responsible for the ultimate burning of the coal, even if it is burned by a third party, and
this will result in increased greenhouse emissions, which in turn contributes to climate change.
In his judgement, Preston took a broad view and readily connected these causal dots, ruling that:
The Project’s cumulative greenhouse gas emissions will contribute to the global total of GHG concentrations in the atmosphere. The global total of GHG concentrations will affect the climate system and cause climate change impacts. The Project’s cumulative GHG emissions are therefore likely to contribute to the future changes to the climate system and the impacts of climate change.
Other courts (such as in Queensland, where the proposed Adani coalmine has successfully cleared various legal hurdles) have tended to take a narrower approach to statutory interpretation, with climate change just one of numerous relevant factors under consideration. In contrast, Preston found climate change to be one of the more important factors to consider under NSW legislation.
To rule against a coalmine on climate grounds, the court also needs to resist the “market substitution” argument – the suggestion that if the proponent does not mine and sell coal, someone else will. This argument has become a common “defence” in climate litigation, and indeed was advanced by Gloucester Resources in the Rocky Hill case.
Preston rejected the argument, describing it as “flawed”. He noted that there is no certainty that overseas mines will substitute for the Rocky Hill coalmine. Given increasing global momentum to tackle climate change, he noted that other countries may well follow this lead in rejecting future coalmine proposals.
He also stated that:
…an environmental impact does not become acceptable because a hypothetical and uncertain alternative development might also cause the same unacceptable environmental impact.
There should be no doubt that this is a hugely significant ruling. However, there are several caveats to bear in mind.
First, there are avenues of appeal. In the absence of a robust legislative framework prohibiting mining operations, it is ultimately up to a court to interpret legislation and weigh up the relevant factors and evidence. The NSW Land and Environment Court has a strong history of progressive judgements, and it is not certain that this example will be followed more widely in other jurisdictions. That said, Preston’s reasoning is firmly grounded in an analysis of the relevant scientific and international context, and should be a highly persuasive precedent.
Second, it is also important to remember that this judgement arose from an initial government decision to refuse the mine, whereas many other legal challenges have arisen from a mining approval.
Finally, climate change was not the only ground on which the mine was rejected. The proposed mine would have been close to a town, with serious impacts on the community.
Nevertheless, this decision potentially opens up new chapter in Australia’s climate litigation history. Preston’s ruling nimbly vaults over hurdles that have confounded Australian courts in the past – most notably, the application of the market substitution defence.
It is hard to predict whether his decision will indeed have wider ramifications. Certainly the tide is turning internationally – coal use is declining, many nations have set ambitious climate goals under the Paris Agreement, and high-level overseas courts are making bold decisions in climate cases. As Preston concluded:
…an open cut coal mine in this part of the Gloucester valley would be in the wrong place at the wrong time… the GHG emissions of the coal mine and its coal product will increase global total concentrations of GHGs at a time when what is now urgently needed, in order to meet generally agreed climate targets, is a rapid and deep decrease in GHG emissions.
Indeed, it is high time for a progressive approach to climate cases too. Hopefully this landmark judgement will signal the turning of the tides in Australian courts as well.
But a global review of insect research has found another casualty: 40% of insect species are declining and a third are endangered. It confirms what many have been suspecting: in Australia and around the world, arthropods – which include insects, spiders, centipedes and the like — appear to be in trouble.
The global review comes hard on the heels of research published in the Proceedings of the National Academy of Sciences USA that suggests a potent link between intensifying heat waves and stunning declines in the abundance of arthropods.
If that study’s findings are broadly valid – something still far from certain – it has chilling implications for global biodiversity.
In the mid-1970s, researchers on the Caribbean island of Puerto Rico conducted a large-scale study to measure the total biomass (living mass) of insects and other arthropods in the island’s intact rainforests, using sweep nets and sticky-traps.
Four decades later, another research team returned to the island and repeated the study using identical methods and the same locations. To their surprise, they found that arthropod biomass was just one-eighth to one-sixtieth of that in the 1970s – a shocking collapse overall.
And the carnage didn’t end there. The team found that a bevy of arthropod-eating lizards, birds and frogs had fallen sharply in abundance as well.
In the minds of many ecologists, a widespread collapse of arthropods could be downright apocalyptic. Arthropods pollinate some of our most important food crops and thousands of wild plant species, disperse seeds, recycle nutrients and form key links in food chains that sustain entire webs of life.
This ecological ubiquity arises because arthropods are so abundant and diverse, comprising at least two-thirds of all known species on Earth. In the 1940s, evolutionary biologist J. B. S. Haldane quipped that “God has an inordinate fondness for beetles.” Humans might think we rule the world, but the planet really belongs to arthropods.
The researchers who documented the arthropod collapse in Puerto Rico considered a variety of possible causes, including pesticides and habitat disruption. But the evidence kept pointing to another driver: rising temperatures.
Weather stations in Puerto Rico indicate that temperatures there have risen progressively in the past several decades – by 2℃ on average.
But the researchers are far less worried about a gradual increase in temperature than the intensification of heat waves—which have risen markedly in Puerto Rico. This is because nearly all living species have thresholds of temperature tolerance.
For example, research in Australia has shown that at 41℃, flying foxes become badly heat-stressed, struggling to find shade and flapping their wings desperately to stay cool.
But nudge the thermometer up just one more degree, to 42℃, and the bats suddenly die.
In November, heat waves that peaked above 42℃ in north Queensland killed off almost a third of the region’s Spectacled Flying Foxes. The ground beneath bat colonies was littered with tens of thousands of dead animals. Dedicated animal carers could only save a small fraction of the dying bats.
El Niño events – fluctuations in Pacific sea-surface temperatures that drive multi-year variations in weather across large swaths of the planet – are also part of this story. New research appears to be resolving longstanding uncertainties about El Niños and global warming.
Recent studies published in Nature and Geophysical Research Letters suggest global warming will in fact intensify El Niños – causing affected areas to suffer even more intensively from droughts and heat waves.
And this ties back to Puerto Rico, because the researchers there believe a series of unusually intense El Niño heatwaves were the cause the arthropod Armageddon. If they’re right then global warming was the gun, but El Niño pulled the trigger.
Puerto Rico is certainly not the only place on Earth that has suffered severe declines in arthropods. Robust studies in Europe, North America, Australia and other locales have revealed big arthropod declines as well.
And while climatic factors have contributed to some of these declines, it’s clear that many other environmental changes, such as habitat disruption, pesticides, introduced pathogens and light pollution, are also taking heavy tolls.
So, at a planetary scale, arthropods are suffering from a wide variety of environmental insults. There’s no single reason why their populations are collapsing.
The bottom line is: we’re changing our world in many different ways at once. And the myriad little creatures that play so many critical roles in the fabric of life are struggling to survive the onslaught.