A fresh water mass extinction: is it on the horizon?

In this blog I have spoken a lot about how fresh water issues such as scarcity and contamination have affected humans, but with the recent release of WWF’s Living Planet Report it seems like a good time to discuss the effect these problems have on fauna and freshwater ecosystems.

Despite covering less than 1% of the Earth’s surface, freshwater contains a disproportionate amount of species, almost 6% in fact (at least 100,000), including around a third of all vertebrates. However there is no doubt that they are under threat, largely, if not entirely, down to human activity. Strayer and Dudgeon, 2010 state habitat degradation, pollution, flow regulation and water extraction, fisheries over exploitation and alien species introduction as the primary causes of this, and there is an increasingly overwhelming case for adding climate change to this list. The Living Planet Index revealed that global populations of vertebrate species had decreased by 58% between 1970 and 2012 with the decline being much more severe in the freshwater ecosystem (81% - as shown in the following diagram) compared to terrestrial (38%) and marine (36%).  

Source: Living Planet Report, WWF.

The fact that 1970 is the starting point of this study makes it likely that significant reductions in population of freshwater species had already occurred. After the Second World War, the building of dams proliferated peaking at around 5500 large dams being constructed per year in the 1970s (Jones, 2014) and although the effects of these are hard to predict, flow interruption can have negative effects on the ecological integrity of flood plain rivers due to changes to patterns of flooding and degradation of downstream channels (Ward and Stanford, 1995) as well as blocking migratory species, and creating calm bodies of water with different temperatures to rivers that may favour different species whilst encumbering others. Dams also block sediment transport which can prevent vital nutrients reaching floodplain soils (Holland, 2016). There were also fewer regulations on industry back then which allowed the likely increased contamination of waterways and in turn habitat degradation.

Since 1970, dam building has remained a driver of this diminution as although construction has reached somewhat of a standstill in Europe and USA, it is still prevalent in developing nations such as China, Brazil and India and there is now 10,000km³ of freshwater stored in dam reservoirs, a staggering five times the amount in surface rivers. The reason for this vast amount of water being needed is of course the increasing consumption of freshwater by humans that has occurred in line with population increases (although these increases were also taking place pre-1970). The following image shows dams being planned and in construction: 

Another side effect of this population rise is the over exploitation of fisheries that has taken place due to an ever-increasing demand for food. This mainly refers to the unsustainable harvest of fish from freshwater, but indirect over exploitation can occur as other species are inadvertently caught in fisheries. Studies have concluded that inland waterways and ecosystems have been poorly managed, and that fish stocking has been prioritised over habitat management (Aps, Sharp, and Kutonova, 2004) which in the long term has resulted in declined numbers.

In terms of how pollution can affect fresh water ecosystems, it is similar to as mentioned in the previous blog post on water contamination. Pollutants can include chemicals and pesticides, raw sewage, petroleum and even thermal discharge. Toxic chemicals, such as PAHs (polycyclic aromatic hydrocarbons) and PCBs (polychlorinated biphenyl) released from industry, and pesticides can have a range of life-threatening effects on aquatic creatures. Depletion of oxygen levels can be triggered by nutrients from agricultural runoff causing eutrophication, as well as the decomposition of faecal matter (WWAP, 2006).

In 1970 when data collection for the LPI started, climate change would not have been considered one of the primary threats to global populations of wildlife. But as carbon dioxide emissions continue to increase and global temperatures exceed 1°C above pre-industrial levels, it can no longer be ignored. Fresh water ecosystems are especially vulnerable to climate change because the species which inhabit them are largely unable to move to a different environment as theirs changes. On top of this, fresh water temperature and abundance are both climate dependent – increased global temperatures can lead to droughts and additional strain being placed on rivers and wetlands with unsustainable extraction levels in order to irrigate crops. This can result in these areas drying up with obvious loss of habitat.

So is there is a solution to this worrying problem of population and species decline?

First of all, it makes sense to protect river and lake ecosystems which are currently untouched. As for those regions which have already been affected by human activity, reconciliation ecology is a term that has been used to ‘encourage biodiversity in human-dominated ecosystems’. It is a recognition that destruction of habitat takes its toll on species. Although it generally applies to smaller, novel ecosystems, this concept is important in changing mind sets towards preservation.

The LPI notes an increase in migratory fish species since 2006, which it puts down to improving water quality in regions such as Europe, and fish passes being added to man-made obstructions to allow migrating fish to move through. If these could be applied globally, especially in the previously mentioned nations where dam construction is still widespread and water quality is generally lower, then it could have a huge effect. Restoration of ecosystems to the condition they were in before humans interacted with them is largely unrealistic, but dam removal projects are the closest thing to this. A number of these have taken place in the USA, where outdated structures are removed often leading to environmental restoration, although due to the huge demand for freshwater from humans it is impossible to make dam removal a widespread process.

There are definite steps forward but the danger is that they are being overwhelmed by the setbacks which could lead to a mass extinction of freshwater species.

Bottled water… a scam or a real threat?

With a global market value of over $150 billion, it is the world’s best-selling soft drink, with a staggering 1 million bottles produced per minute, worldwide. So why has something that is no better than the liquid which comes out of our taps, but can cost 300-1000 times more, become so popular and what are the effects of this on our planet and society?

Tap water in developed countries such as the UK is cheap with the average daily use of 150 litres costing around 21 pence, and regulated to make sure it is of the requisite quality. So why would anyone choose to pay a premium for a small amount of bottled water? The answer lies in how it has been marketed. Companies promote the idea that their product tastes better than tap water, even though blind taste tests have often shown there is no difference. A quick google search shows there is an abundance of different products, with varying claims about what their water can offer (even going as far as claiming to be ‘Earth’s Finest Water’). In reality, they may have differing mineral contents but the differences in taste would be subtle. Between 25-30% of bottled water products are actually just standard municipal water that has been treated, reminiscent of a certain Only Fool's and Horses episode...

Its popularity may also be in part due to a recent push towards healthier lifestyles as people replace sugary soft drinks such as Coca-Cola with bottled water. This is positive in that it cuts the amount of calories in people’s diets (an estimated 74 a day on average in the USA) which has obvious health benefits, but the point remains that the sugary drinks could be replaced with tap water, rather than bottled water. Many of the purchases may also be based upon buying the actual bottle, rather than the water itself, as convenience and cost were shown to be two of the primary factors in decision making when buying bottled water (Ward et al., 2009).

There are negative environmental effects stemming from the bottled water industry too. The single-use bottles which are a regular component of many people’s lunch are made of the plastic polyethylene terephthalate (PET) which requires a large amount of oil to produce. This of course produces the greenhouse gas carbon dioxide, with 6kg of CO2 released for every 1kg of plastic (enough for around 50 water bottles) made as well as the extra released during everything from transportation to chilling the water for consumption. In contrast, Thames water estimate that to produce a litre of their water 0.0003kg of CO2 is released. Water is also used in the production process of bottled water, with estimates of up to 3 litres of water used to produce 1 litre of bottled water. On top of this, only about 25% of plastics are recycled with the remainder entering landfill (taking hundreds of years to decompose), being incinerated (producing yet more CO2) or ending up littering the world’s oceans posing a hazard to many marine life forms. The Great Pacific garbage patch - a gyre of marine debris that comes from both North America and Asia and consists of mostly plastics – has been estimated to be twice the size of Texas, and will only keep growing as more and more plastic bottles are used and thrown away.

Source: Marine Debris

A recent study by Jamieson et al., 2017 also highlighted the dangers of microplastics, which includes the plastics manufactured to be tiny and that are included in various cosmetic products, and those that result from degradation of larger pieces of plastic. These microplastics have been shown to infiltrate even the deepest parts of the ocean, with levels of 'persistent organic pollutants' in some amphipods in the Mariana Trench exceeding levels commonly found in highly polluted industrial areas.

As discussed in previous posts, around 10% of the world’s population does not have access to clean drinking water. One of the UN’s sustainable development goals was to ensure everyone has access to clean and safe water source by 2030, and surely some of the amount unnecessarily spent on bottled water annually would go a long way towards delivering this.

Filling reusable bottles with tap water would be an obvious step forward in reducing the purchasing that we see today. The recent 5p charge on plastic carrier bags in England has seen reductions in use of around 70% and there are also schemes in other EU countries to reduce waste such as a deposit being placed upon bottles meaning they can be returned to the producer and refilled. Similar arrangements could go a long way to reducing plastic bottle use in the UK, as well as other developed nations.