Deep impact – the plastic on the seafloor; the carbon in the air

We live in a geological age defined by human activity.  We live during a time when the landscape of the earth has been transformed by men, its surface paved and cut, its vegetation manipulated, transported and ultimately replaced. A time when the chemical composition of the atmosphere, the rivers and the oceans has been changed – in some ways that are unique for the past million years and in other ways that are unprecedented in Earth history. In many ways, this time is defined not only by our impact on nature but by the redefinition of what it means to be human.

From a certain distance and perspective, the transformation of our planet can be considered beautiful. At night, the Earth viewed from space is a testament to the ubiquitous presence of the human species: cities across the planet glow with fierce intensity but so do villages in Africa and towns in the Midwest; the spotlights of Argentine fishing boats, drawing anchovies to the surface, illuminate the SW Atlantic Ocean; and the flames of flared gas from fracked oil fields cause otherwise vacant tracts of North Dakota to burn as bright as metropolises.

Environmental debates are a fascinating, sometimes frustrating collision of disparate ideas, derived from different experiences, ideologies and perspectives.  And we learn even from those with whom we disagree.  However, one perspective perpetually bemuses and perplexes me: the idea that it is impossible that man could so transform this vast planet. Of course, we can pollute an estuary, cause the Cuyahoga River to catch fire, turn Victorian London black or foul the air of our contemporary cities.  We can turn the Great Plains into cornfields or into dust bowls, the rainforest into palm oil plantations, swamplands into cities and lowlands into nations.  But these are local.  Can we really be changing our oceans, our atmosphere, our Earth that much?

Such doubts underly the statements of, for example, UKIP Energy Spokesman Roger Helmer:

 ‘The theory of man-made climate change is unproven and implausible’.

It is a statement characterised by a breathless dismissal of scientific evidence but also an astonishingly naive view of man’s capacity to impact our planet. And it is a statement that has been increasingly echoed by those in the highest echelons of power.

There are places on Earth where the direct evidence of human intervention is small. There are places where the dominance of nature is vast and exhilarating and awe-inspiring.  And across the planet, few places are entirely immune from reminders – whether they be earthquakes or volcanoes, tsunamis or hurricanes – that nature is vast and powerful.

But the Earth of the 21st century is a planet shaped by humans.


A powerful example of humanity’s impact on our planet is our Plastic Ocean.  We generate nearly 300 billion tons of plastic per year, much of it escaping recycling and much of that escaping the landfill and entering our oceans. One of the most striking manifestations of this is the vast trash vortex in the Northern Pacific Gyre. The size of the vortex depends on assumptions of concentration and is somewhat dependent on methodology, but estimatesrange from 700 thousand square kilometres to more than 15 million square kilometres.  The latter estimate represents nearly 10% of the entire Pacific Ocean.   Much of the plastic in the trash vortex – and throughout our oceans – occurs as fine particles invisible to the eye.  But they are there and they are apparently ubiquitous, with concentrations in the trash vortex reaching 5.1 kg per square km*.  That’s equivalent to about 200 1L bottles.  Dissolved.  Invisible to the eye.  But present and dictating the chemistry of the ocean.

More recently, colleagues at Plymouth, Southampton and elsewhere illustrated the widespread occurrence of rubbish, mainly plastic, on the ocean floor.  Their findings did not surprise deep sea biologists nor geologists; we have been observing our litter in these supposedly pristine settings since some of the first trips to the abyss.

My first submersible dive was on the Nautile, a French vessel that was part of a joint Dutch-French expedition to mud volcanoes and associated methane seeps in the Mediterranean Sea.  An unfortunate combination of working practice, choppy autumn seas and sulfidic sediments had made me seasick for most of the research expedition, such that my chance to dive to the seafloor was particularly therapeutic. The calm of the deep sea, as soon as we dipped below the wave base, was a moment of profound physical and emotional peace.  As we sank into the depths, the light faded and all that remained was the very rare fish and marine snow – the gently sinking detritus of life produced in the light-bathed surface ocean.

As you descend, you enter a realm few humans had seen…. For a given dive, for a given locale, it is likely that no human has preceded you.

Image from Nautile Dive to the Mediterranean seafloor.  Shown are carbonate crusts that form where methane has escaped to the seafloor as well as tube worms thriving on the chemical energy available in such settings.  Plastic debris has been circled in the upper right corner.

Mud volcanoes form for a variety of reasons, but in the Mediterranean region they are associated with the tectonic interactions of the European and African continents.  This leads to the pressurised extrusion of slurry from several km below the bottom of the sea, along mud diapirs and onto the seafloor. They are commonly associated with methane seeps; in fact a focus of our expedition was to examine the microbes and wider deep sea communities that thrive when this methane is exposed to oxidants at the seafloor – a topic for another essay. In parts of the Mediterranean Sea, they are associated with salty brines, partially derived from the great salt deposits that formed in a partly evaporated ocean about five and a half million years ago.

And all of these factors together create an undersea landscape of indescribable beauty.

On these mud volcanoes are small patches, about 20 cm wide, where methane escapes to the seafloor.  There, methane bubbles from the mud or is capped by thick black, rubbery mats of microorganisms.  Ringing these mats are fields of molluscs, bouquets of tube worms, great concrete slabs of calcium carbonate or white rims of sulphide and the bacteria thriving on it. Streaming from these seeps, down the contours of the mud cones, are ribbons of ultra-dense, hypersaline water.  The rivulets merge into streams and then into great deep sea rivers. Like a photonegative of low-density oil slicking upon the water’s surface, these are white, high-density brines flowing along the seafloor.  Across the Mediterranean Sea, they pool into beautiful ponds and in a few very special cases, form great brine lakes.

And two kilometres below the seafloor, where humans have yet to venture our rubbish has already established colonies. Plastic bottles float at the surface of these lakes; aluminium cans lie in the mud amongst the microbial mats; between those thick slabs of calcium carbonate sprout colonies of tube worms and the occasional plastic bag.

We have produced as much plastic in the past decade as we have in the entirety of the preceding human history.  But the human impact is not new.  On our very first dive, we observed a magnificent amphora, presumably of ancient Greek or Roman origin and nearly a metre across, half buried in the mud.


Today the human footprint is ubiquitous. Nearly 40% of the world’s land is used for agriculture – and over 70% of the land in the UK.  Another 3% of the land is urbanised.  A quarter of arable land has already been degraded.

There are outstanding contradictions and non-intuitive patterns that emerge from a deeper understanding of this modified planet.  Pollinators are more diverse in England’s cities than they are in our rural countryside.  One of the most haunting nature preserves on our planet is the Demilitarized Zone between North and South Korea – fraught with landmines but free from humans, wildlife now dominates. And of course, although global warming will cause vast challenges over the coming centuries, that is largely due to one human impact (greenhouse gas emissions) intersecting with another (our cities in vulnerable, low-lying areas and our borders and poverty preventing migration from harm).   And on longer timescales, we have likely spared our descendants of 10,000 years from now the hassle of dealing with another Ice Age.

But there can be no doubt or misunderstanding –  we have markedly changed the chemical composition of our atmosphere.  Carbon dioxide levels are higher than they have been for the past 800,000 years, perhaps the last 3 million years.  It is likely that the last time the Earth’s atmosphere contained this much carbon dioxide, glyptodons, armadillo-like creatures the size of cars, roamed the American West, and hominids were only beginning the first nervous evolutionary steps towards what would eventually become humanity. Methane concentrations are three times higher than they were before the agricultural and industrial revolutions.  Also higher are the concentrations of nitrous oxides.  And certain chlorofluorcarbons did not even exist on this planet until we made them.

The manner in which we have changed our planet has – at least until now – allowed us to thrive, created prosperity and transformed lives in ways that would have astonished those from only a few generations in the past.  It is too soon to say whether our collective impact has been or will be, on the whole, either ‘good’ or ‘bad’ for either the planet or those of us who live upon it. It will perhaps never be possible to define such a complex range of impacts in simple black and white terms.  But there is no doubt that our impact has been vast, ubiquitous and pervasive.  And it is dangerous to underestimate even momentarily our tremendous capacity to change our planet at even greater rates and in even more profound ways in the future.

*Moore, C.J; Moore, S.L; Leecaster, M.K; Weisberg, S.B (2001). “A Comparison of Plastic and Plankton in the North Pacific Central Gyre”. Marine Pollution Bulletin 42 (12): 1297–300. doi:10.1016/S0025-326X(01)00114-X. PMID 11827116.

Tackling climate change is fundamentally a question of justice

This is one of my very first blogs, co-authored with friend and colleague Patricia Lucas.  It was written for Business Fights Poverty (hence the questions at the end), and it stakes out the central themes of my research then and now: that the biggest challenge climate change poses is a world with profoundly greater uncertainty – and with that, confusion, opportunism and victimisation; and that it is the poor and vulnerable who will bear these risks.
Tackling climate change is fundamentally about justice.  About fairness. About equality.
In September 2013, the IPCC published the Fifth Annual Report on the Physical Basis of Climate Change.  It devotes little attention to the human and ecological impacts of global environmental and climatic change, topics that will be addressed by working group reports released in early 2014 .  Nonetheless, the trajectory of climate and other environmental changes and their implicit impacts on society are stark. Despite numerous treaties and efforts at mitigation, concentrations of carbon dioxide and other greenhouse gases continue to increase, and at greater rather than diminished rates. If those rates continue they will result in global warming of 3 to 5.5°C by 2100. This in turn, will result in dramatic changes to the global hydrological cycle, including both more evaporation and more rainfall.
A More Uncertain Climate
Flood; photo by Paul Bates

The results will be a more hostile climate for many as land can become either drier or more flood-prone or both, changes exacerbated in coastal areas by sea level rise.  Freshwater supply will also be affected by the forecast changes in climate. The quantity of water flowing in glacier or snow-melt fed river basins will change, affecting around a sixth of the world’s population[i], while coastal freshwater will be contaminated with saline water[ii]. Areas of the Mediterranean[iii], Western USA[iv], Southern Africa[v] and North Western Brazil[vi] are projected to face decreased availability of freshwater.

Key to understanding who will be affected is our ability to predict changes in rainfall, seasonality, and temperature at a regional scale.  However, regional climatic predictions are the most challenging and least certain, especially with respect to the nature and amount of rainfall. For vast parts of the world, including much of South America, Africa and SE Asia, it is unclear whether climate change will bring about wetter or drier conditions. Thus, uncertainty will become the norm: uncertainty in rainfall; uncertainty in weather extremes and seasonality; and most importantly, uncertainty in water resources.

Those combined effects lead to an additional and perhaps the most profound uncertainty for the latter half of the 21st century: uncertainty in food production and access. In the absence of other factors, climate uncertainty and more common extreme events will compromise agriculture at all scales, yielding increased food prices and increased volatility in markets.

Impacts on the Poor

Although the human impacts of climate change will be diverse, their effects will be worst for the most impoverished and, by extension, least resilient population groups.  The UN reports that climate change could “increase global malnutrition by up to 25% by 2080.”  And all of this occurs against a backdrop in which access to food is already a challenge for the poorest of the world already a challenge for the poorest of the world [p5], a situation exacerbated by the global financial crash.These risks to the poorest result from a lack of resources to mitigate harm, lack of power to protect resources, and the global competition for resources.
Those who lack the financial resources to migrate or build more hazard-resistant homes will suffer most from extreme events, as has been sharply illustrated by those suffering most in the aftermath of Typhoon Haiyan.  Those who can least afford to dig deeper wells into more ancient aquifers as water resources diminish will go thirsty.  Subsistence farmers – and those dependent on them – are less resistant to climate shocks (desertification) and adverse weather events (flooding) than commercial farmers.
Land ownership for the poorest is often tenuous, and displacement from land a serious problem for many.  Previous switches to biofuels have led to land competition, resulting in both loss of land to subsistence [p6]  farmers, and diversion of commercial production leading to shortages [p7]  and increased food prices. Within communities, these effects are not evenly spread as marginalised groups, such as women, are the least likely to hold land tenure [p8] .  Similarly, there is increased competition for water [p9]  between peoples, but also between water for industry (including agriculture) and water for drinking. When water is scarce, pollution of fresh water is common, and governance is weak, the poorest are likely to lose out.
Food security comes in many forms, reflecting not just climate and environment but culture, politics and other social constructs. Image by Mammal Research Unit, University of Bristol

Food competition will most likely be exacerbated by other factors: rising demand from a rapidly expanding population and a growing demand for meat from a global ‘middle class’; the increased economic divide between post-industrial and developing nations; the ongoing depletion of soil nutrients and associated impacts on the nutritional value of our food.  The combination of these factors will result in profound impacts on food security. Who decides what gets grown? Who can afford it in the context of global markets and the loss of agricultural land? The poorest members of even the wealthiest societies are the most vulnerable to dramatic and unpredictable changes in food costs[p10] .

‘Wicked Problems’

These issues yield a profoundly challenging ethical issue: the wealthy who are most responsible for anthropogenic climate change, via the greatest material consumption and energy demand, have the greatest resilience to food market fluctuations and the greatest means for avoiding their most deleterious impacts.  Therefore, these issues challenge all governments to dramatically and swiftly act to decrease greenhouse gas emissions and mitigate the associated climate change.
Unfortunately, many proposed mitigation strategies could also have negative consequences for food prices and availability. Increasing energy prices, such as those brought about by a carbon tax, will be passed onto food prices.  Genetically modified foods could be essential to feeding a growing population, and we would urge that future efforts expand to incorporate a greater degree of climate resilience in crops; however, the patents on those crops can make them financially inaccessible to the poorest nations or build critical dependencies.
Although sustainable agriculture and crops might reduce the impact of climate change and uncertainty in some countries, these solutions can be deleterious for the poorest.  They are more likely to live in regions and areas most negatively affected by climate change, most likely to be relying on subsistence/small scale agriculture and least likely to have access to the global market as consumers.  In other words, a stable global market will be of little direct benefit to them; in fact, most of these populations are likely to face competition for land/water use from globalised markets (for biofuels or commercial farming).  In short, what builds food resilience in one nation might be exposing the most economically vulnerable in another.
In fact, when properly mobilised for the benefit of the community, access to new energy sources – even if in the form of fossil fuels – can be transformative and facilitate the economic growth needed to access increasingly globalised food markets [p12].    Domestic access to gas reduces the need to collect wood for fires, reducing deforestation, improving air quality, and freeing up time for communities to address other development needs.
This is not an argument against mitigation of climate change, far from it!  We must continuously and aggressively try to minimise the harm that climate change will cause.  But it does need to be balanced against human development needs, and this represents one of the world’s most profound challenges. In some circles, we consider this a ‘wicked’ problem: a problem that has multiple causes, probably in interaction, and where information is incomplete, such that proposed solutions might be incomplete, contradictory, complex and work across multiple causes in complex systems.
Challenges and Opportunities

Wicked problems are not intractable, however, and previous studies of land use for biofuels provide clues as to how a complex solution could be more sustainable for all; well planned switches to biofuels which consider local custom in land tenure can provide more land for agriculture, and reduce deforestation pressure.

In such situations, we argue, solutions which focus on halting or slowing climate change alone, and then coping with the business and development problems that they might create answer the wrong question.  Our challenge to the business (and academic) community, then, is to engage with some wicked questions:

  • What are the business opportunities in improving the social and physical environment?
  • Can the global agricultural system be a single resilient network, rather than a competition?
  • What technology or innovation is needed to support a resilient food network?
  • How can innovative solutions to these challenges generate local income, allowing reinvestment in education and development?
These are difficult questions but they also represent opportunities for development and growth in poor communities.  A world with increasing environmental uncertainty is a challenge for both businesses and vulnerable communities.  But it could also be a shared opportunity for growth and development: to innovate and identify new solutions, to co-invest in local resilience and risk reduction, and to share the growth that arises from more stable communities.

[i] Z Kundzewicz, L Mata, N Arnell, P Doll, P Kabat, K Jimenez, K Miller, T Oki, Z Sen & I Shiklomanov, Freshwater Resources and their Manegemtn. Climate Change 2007: Impacts, Adaption and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press2007
[ii] R Buddemeier, S Smith, S Swaaney & C Crossland, The Role of the Coastal Ocean in the Disturbed and Undisturbed Nutrient and Carbon Cycles,  LOICZ Reports and Studies Series2002, 84
[iii] P Etchevers, C Golaz, F Habets & J Noilhan, Impact of a Climate Change on the Rhone River Catchment Hydrology,Journal of Geophysical Research2002, 4293
[iv] J Kim, T Kim, R Arritt & N Miller, Impacts of Increased CO2 on the Hydroclimate of the Western United States, Journal of Climate2002, 1926
[v] M Hulme, R Doherty & T Ngara, African Climate Change, Climate Research2001, 145
[vi] J Christensen, B Hewitson, A Busuioc, A Chen, X Gao, I Held, R Jones, R Kolli, W Kwon, R Laprise, V Magana Rueda, L Mearns, C Menendez, J Raisanen, A Rinke, A Sarr & P Whetton, Regional Climate Change, The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change,2007, 847
This blog is written by Prof Rich Pancost, Director of the Cabot Institute and Dr Patricia Lucas, School for Policy Studies, both at University of Bristol.
Dr Patricia Lucas
Prof Rich Pancost
This blog has kindly been reproduced from the Business Fights Poverty blog.

Ancient global warming caused extreme rainfall events

Some reflections by my co-authors and me on our recent paper in Earth and Planetary Science Letters, showing that ancient global warming was associated with an increase in the number of extreme rainfall events and this had a profound impact on the land and coastal seas.

The Palaeocene-Eocene Thermal Maximum (PETM), which occurred about 56 Million years ago, is of great interest to climate scientists because it represents a relatively rapid global warming event, with some similarities to the human-induced warming of today.  Although there have been many investigations of how much the Earth warmed at the PETM (about 5 to 8C), there have been relatively few studies of how that changed the hydrological cycle.  This newly published work shows that rainfall increased in some places and decreased in others, according to expectations, but that much of the world experienced more intense and episodic (or ‘flashy’) rainfall events.

Lead author Matt Carmichael (School of Chemistry and School of Geographical Sciences) explained: ‘With the same climate models used to study future climate change, we studied how a doubling of carbon dioxide concentrations would affect rainfall patterns on a world with Eocene geography. This increased the overall global precipitation – warmer air holds more water.  But it also changed the pattern and frequency of extreme events.  The tropics became wetter and the incidence of extreme events increased, by as much as 70% in some tropical regions. In other places, total annual precipitation and the number of extreme events became decoupled; in other words, those areas became drier, with less frequent but more extreme events.  All of this illustrates the complexity of how global warming will affect our local, regional and global rainfall patterns.’

Co-author Professor Rich Pancost (School of Earth Sciences), explained how these findings agree with a range of geological and chemical features of the Palaeocene-Eocene global warming: ‘This warming event is associated with major changes in how soil and sediment were eroded and moved around the landscape.  In many places, river systems that had been transporting silt or sand became associated with fist-sized rocks or even boulders; and more sediment was transported to and buried in coastal margins. In some locations, the rate of sediment accumulation increased by a factor of ten. But at the same time, there is also evidence that these systems became more arid.  Our climate simulations reconcile this; many locations do experience an increase in aridity but also more intense rainfall events.  Those events were likely responsible for increased energy in these systems, moving around more material and larger objects. Ultimately it flushed more sediment to the ocean, causing eutrophication, blooms of algae and in some cases hypoxia.’ [Analogous but less severe than Oceanic Anoxic Events.]

Photo of the Claret Conglomerate by Rob Duller, University of Liverpool.  I wrote about this here: “In central Spain, outcropping on dusty hillsides overlooking apparently endless miles of gnarled olive trees, is the Esplugafreda Formation. The Formation consists of hundreds of metres of rusty-coloured palaeosols and the remains of ancient channels, part of a more-than-55-million-year-old braided river system. What is particularly striking about these rocks is that atop them sits the Claret Conglomerate, a unit not of silt, sand and ancient soil, but of pebbles, fist-sized stones and even boulders. These stones are part of the same river system but were deposited under conditions with far more energy: the Conglomerate represents a relatively transient moment in Earth history of remarkably intense rainfall events. And these events were probably caused by ancient global warming.”

Co-author Professor Dan Lunt (School of Geographical Sciences) elaborated on this: ‘There are many similar events in Earth history, where warming appears to have been associated with changes in rainfall and sedimentary systems.  Although we have not investigated them here, it is very likely that our results are translatable – because the physics that underpins them remains the same.  Thus, the collective body of research confirms that global warming in the past and the future will be associated with more ‘flashy’ rainfall, with implications for flooding and water management.’

Professor Pancost elaborated: ‘Past climate has lessons for our future.  Not only do the models show evidence for more intense rainfall events – with all of the associated implications – but they are consistent with all of our other data. In fact, they explain inconsistencies in our other data and confirm some long-established hypotheses. In doing so, they foreshadow our potential future with complex and dramatic changes in rainfall, more flooding and more soil erosion.’

Response of the hydrological cycle to doubling of carbon dioxide concentrations:

Fig. 2

From the paper: Figure a shows the expected impact of a doubling of CO2 on global precipitation patterns – dry areas get drier and wet areas get wetter. However, (b) shows that the number of actual precipitation events decreases almost everywhere.  Both (c) and (d) show different mathematical expressions of ‘extreme’ events, and both show that nearly global increase in the number of extreme events.

The article is: Carmichael, M., Pancost, R.D. and Lunt, D.J. (2018) Changes in the occurrence of extreme precipitation events at the Paleocene-Eocene thermal maximum.  Earth and Planetary Science Letters 501, 24-36.

It is available here: