The Degradation of the 3%


The sun sets over the river Lee, Cork, Ireland

Source: mp2films (private collection)

Our bodies are made of nearly 65% water and we cannot survive on average more than three to four days without drinking freshwater. It

is essential for all life on Earth, however, it constitutes a mere 3%of the earths total water supply with two-thirds of this locked away in frozen glaciers or snow.

As global freshwater sources become more and more degraded each day, it is imperative that as part of a journey from the source of a freshwater stream to the vast expanses of open ocean, to consider the state of the world’s freshwater resource particularly in light of the Anthropocene and Earth's Planetary Boundaries.

The Anthropocene and Earth's Planetary Boundaries

The Anthropocene, as defined in detail and discussed in this blog post, is proposed as the title of the current geological epoch - the age of major human-induced alteration of many of Earth’s systems including the Earth’s freshwater systems. Scientists argue that the human race now rivals environmental and geological processes as we have forced many of the Earth’s systems beyond what is known as its ‘Planetary Boundaries’ (PBs), i.e. the thresholds below which we can 'operate safely'. As you can see below, freshwater use constitutes one of the PBs, the boundary of which is measured as the maximum basin-scale blue water extraction from rivers which avoids 'regime shifts' to ecosystem functioning. Although it is still in the green 'safe zone' according to Steffen et al. (2015), other studies have since shown that we are fast approaching the boundary.




Fig. 1: The revised state of nine planetary boundaries from pre-industrial levels (at the core) to 2015, wherein the green regions indicate the 'safe operating space' for humans; yellow indicates uncertainty and an increase in risk whilst red are the high-risk areas - within which we find ourselves for three planetary boundaries. The planetary boundary of particular interest to Source To Sea is 'Freshwater use', although the interconnections between these boundaries mean they cannot be considered in isolation.

Source: Steffen et al. 2015


Human Water Security

The global water cycle (yes, I am taking it back to primary school with that hyperlink, when life was much simpler) has indeed entered this era, the Anthropocene, as humans are now the dominant driving force changing the Earth’s river flow. Studies have unveiled some stark figures:

Roughly 25% of Earths river basins  dry out before ever reaching the oceans due to our use of freshwater resources in the basins and further upriver.

Almost 80% of the human population is living in an area exposed to high threat levels to freshwater security.

One in ten people do not have access to clean drinking water (that’s 844 million people worldwide or almost one hundred times the population of London).

289,000 children under the age of five die every year from water-related diarrheal diseases - that is 1 child every 2 minutes.

There is something fundamentally wrong here and it is not only affecting the human race: freshwater ecosystems are suffering much greater biodiversity declines than the most impacted terrestrial and marine ecosystems. This means if something does not inherently change in the way we as a species, as a global community and as a society, interact with our home planet, the opportunity to preserve much of the remaining biodiversity will soon be a lost cause.


Fig. 2: "Global geography of incident threat to human water security and biodiversity"

Source: Vorosmarty et al. 2010

The colour gradient on this map indicates threat level and as we go from blue to red the threat level increases. Comparing the upper map to the one at the bottom, notice taht they look almost identical, although they are quantifying threat levels for two different things:

  • Top map: threat level to human water security
  • Bottom map: threat level to biodiversity.

This highlights the central role healthy freshwater systems plays in minimizing both human water security AND unthreatened biodiversity. Regions of the world with intensive agriculture; large population sizes or deserts, show shades of red, whilst uninhabited and remote regions appear blue.

The threat to water security has many driving forces, including pollution (especially organic pollution by wastewater discharge); land cover change and catchment area degradation; irrigation; engineering of river channels and climate change. 


Organic pollution of rivers is increasing globally, predominantly by urbanization, but even more so by the intensification of livestock farming.

Each healthy river system has a certain capacity to alleviate organic pollution stressors through 'self-cleaning' mechanisms - by natural degradation and dilution - in order to reduce downstream effects.

However, this is something that cannot be taken for granted. The self-cleaning capacity is diminishing quickly due to reductions in river discharge, resulting from climate change and water extraction. The accumulation of such organic waste in freshwater systems then promotes the growth of microbial life, which in turn depletes oxygen levels and thus impacts the entire river ecosystem.

Major polluters of waterways in Ireland are added to a watch list by the Environmental Protection Agency, as they are prioritized for enforcement. Five of the seven top polluters on this list are Irish dairy producers, underlining the impact the intensification of agriculture has on river systems.


Untreated sewage flows freely into the ocean in many parts of Ireland.

Photo credit: Declan O'Mahony

A Grand Challenge

Addressing any one of these factors constitutes a grand challenge for both science and policy, particularly the complex interconnections between them. Our modern society’s focus on urbanism and individualism, but primarily its neoliberalism, has abated the fact that we rely on a healthy planet for our own existence and well-being. We have become so disconnected from the natural world that the importance of healthy ecosystems to humans, let alone the intrinsic value of nature, has become sidelined to make room for quick and easy profit making. Many of us live in cities built on rivers and yet choose not to be aware of (nevermind speak out on) how degraded these rivers have become. This choice allows big corporations and governments to continue sidestepping the need to address their major violations against nature.

Evidently, ahead lies a path of challenge and struggle, particularly in light of our growing population, biodiversity loss, climate change and the alteration and degradation of the global freshwater system. However, the human race has shown to be capable of mass revolution, so perhaps there is still a chance, before the other six planetary boundaries are surpassed, to create paradigm shifts and necessary societal restructuring.

But for this to happen, it certainly will take us to wake up, get up, shake the lethargy from our bones and DO SOMETHING.