Humans are causing one of the worst mass extinctions in Earth history

Humans are the root cause of the ‘biological annihilation’ of life on Earth, according to a study published recently in the journal Proceedings of the National Academy of Sciences (PNAS).

The study – conducted by a team of scientists from the National Autonomous University of Mexico and Stanford University – studied population and distribution trends for 27,600 vertebrate species across the globe and found that 32 per cent are decreasing dramatically in both numbers and geographic range.

This study adds to the burgeoning evidence that we are not only witnessing one of the planet Earth’s worst mass extinction events but that we all collectively have blood on our hands.

How do we know that the situation is so serious and that most species will not simply soldier on?

To fully appreciate the scale of this tragedy, we can place the past few centuries within the context of what we know about life during Earth’s 4,543 million-year long history.

Biodiversity in Earth’s ancient past

Generations of scientists from different disciplines – palaeontology, geology and geochemistry, for example – have devoted their lives to reconstructing how life and environmental conditions have changed and become intertwined over time.

A similarly devoted cohort of ecologists and other scientists have been studying modern day species, habitats and ecosystems, looking at the rate of loss of species over time.

Ecologists measure extinction directly in the field, while palaeontologists and other geoscientists do so by digging fossils and extracting evidence from geologic layers of known ages.

Although they use different methods and data, both fields focus on similar questions – What species are present? How many? How do they interact? What causes species to migrate, boom and die off?

The ‘Big 5’

Mass extinction events – the widespread loss of life on our planet in a short period of time – are quite unusual when compared to the gradual ‘background’ extinction rates from the likes of ecological competition, predation and other gradual changes.

We now know that five major extinction events have disrupted the course of life on Earth over the past 600 million years.

The so-called ‘Big 5’ were the end-Ordovician extinction event 443 million years ago (Ma); the Late Devonian event between 370 and 365 Ma; the end-Permian event 252 Ma; the end-Triassic event 201 Ma and the end-Cretaceous event 66 Ma.

Based on the fossil record before and after these events, it is estimated that each of the ‘Big 5’ killed off at least 75 per cent of all life at that time.

These mass extinction events span intervals ranging from a few thousand to hundreds of thousands of years, a blip in geologic time.

The end-Cretaceous event is the most well understood, thanks in large part to the work conducted by the Nobel Prize winning scientist Luis Walter Alvarez and his son Walter.

Along with colleagues, they identified an ‘extraterrestrial’ iridium layer in sedimentary strata from deposits of this age at sites around the globe.

The story became clear when scientists stumbled upon a large impact crater at the Yucatán Peninsula in Mexico – the end-Cretaceous MEE and the last days of the non-avian dinosaurs were brought about by an asteroid impact and the ensuing chain of events.

The Great Dying

The end-Permian extinction, aptly nicknamed ‘The Great Dying’ was the largest and most catastrophic of the ‘Big 5’.

It caused the staggering loss of 95 per cent of marine species and 70 per cent of terrestrial species in a geologic heartbeat – about 20,000 years – according to 2011 study published in Science.

The ‘Great Dying’ resulted from runaway climate change – with global temperatures 8°C warmer than previous – caused by the release of large amounts of CO2 and other greenhouse gases to the atmosphere.

The exact trigger is still debated but it seems likely that massive volcanic eruptions in what is now Siberia and methane released from destabilised deep sea gas hydrates are the primary culprits.

The combined effect would have been a complete change in atmospheric composition, with CO2­ concentrations probably about four or five times higher than today, depletion of oxygen in the oceans and massive sea level rise.

Humans on par with asteroids and mass volcanism

While there have likely been numerous other mass extinction events prior to 600 Ma, the last 600 million years documents the rise and evolution of animal and plant life and all of the trials and tribulations faced with living on Earth.

So how do the ‘Big 5’ compare with extinction since humans have been on the scene?

There is abundant fossil and archaeological evidence that humans have been a primary cause of animal extinction ever since we moved out of Africa between 50,000 and 100,000 years ago.

According to a 2017 study in the journal Nature, the widespread extinction of large terrestrial species has coincided with historical human migrations.

Terrestrial animal extinctions continued unabated to the point that by about 3,000 years ago, it is estimated that 50 per cent of large mammal species and 15 per cent of birds were extinct.

Since 1500 AD extinction rates accelerated as the Age of Exploration brought us to vast new lands.

The International Union for Conservation of Nature (IUCN) now estimates that 338 vertebrate species have gone extinct since 1500 AD.

A 2015 study in the journal Science Advances puts vertebrate extinctions at as much 100 times greater than the calculated background rate of 2 per 100 years.

The IUCN Red List – containing a database of described species and their conservation status – currently contains 80,000 species and almost 30 per cent are threatened with extinction.

Forty-one per cent of amphibians, 34 per cent of conifers, 33 per cent of reef-building corals, 25 per cent of mammals and 13 per cent of birds are currently threatened.

The spread of agriculture is the main driver for most of these losses, followed by the spread of urbanisation, logging, mining, the loss wildlife transport corridors, hunting and water pollution.

Hundreds of species and countless populations are being lost each year as a result of human activity and since countless species have yet to be described, much more are also likely threatened or threatened with extinction.

The Anthropocene and the Sixth Mass Extinction

The greatest mass extinctions in Earth history brought complex life to the very brink of existence in as little as a few thousand years.

Historical and modern pressures from human activity have driven large proportions of species to extinction or to the brink of extinction in a similar, if not more rapid, timeframe.

Scientists may debate whether we are on the cusp or in the middle of the sixth mass extinction and when exactly the Anthropocene geological epoch – where humans have left behind a global identifiable record in the geologic record – began.

Either way, the plight of most species on Earth has reached crisis level and is set to escalate in the coming years as the human population potentially balloons by another four billion by the end of the twenty-first century and climate change will play an increasingly greater role in species extinction.

Urgent conventional and proactive conservation approaches are needed, together with an unprecedented degree of engagement between stakeholders, scientists and policy makers.

 A version of this article appeared in the Green News on July 21st, 2017.
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New project launched to study links between flooding and waterborne disease outbreaks

A new research project investigating the links between flooding events and the incidence of waterborne infectious disease outbreaks in Ireland was officially launched at UCD Earth Institute today.

The multidisciplinary project will involve social scientists, environmental scientists, engineers and public health researchers from UCD, University of Limerick, DIT and Trinity College.

Flood damage to infrastructure receives widespread media attention but the potential public health consequences for society from future increased flooding as a result of climate change has received little consideration.

A major public health concern, according to Dr Eoin O’Neill from UCD Earth Institute and principal investigator of the project, is that more intense or prolonged rainfall events can mobilise viral and bacterial pathogens from agricultural and domestic sources, transmit them to rivers and groundwater and increase the incidence of waterborne infectious diseases.

Previous research conducted by Dr. Jean O’Dwyer, a UL-based collaborator on the project, has already shown that increased rainfall in Ireland increases the likelihood of groundwater contamination with the familiar pathogen E. coli. 

The project aims to quantify the effects of intensive rainfall and flooding on the incidence and severity of pathogens and to identify the knowledge and awareness gaps of well owners and users in relation to drinking water sources and flood awareness and preparedness.

It is hoped that this project will help reduce the occurrence of illnesses caused by waterborne diseases, such as gastrointestinal illness.

The project will provide an evidence base to inform policy and practice and develop guidelines to inform public authorities when responding to extreme weather conditions.

According to Dr Paul Hynds – an epidemiologist based in DIT and a collaborator on the project: “This should be of particular interest to Irish policymakers including the Environmental Protection Agency (EPA) and Office of Public Works (OPW) as 800,000 Irish people rely on a private unregulated groundwater source (wells) for daily water consumption, in addition to many holidaymakers.”

The project is funded by the Geological Survey of Ireland and the Irish Research Council.

A version of this article appeared in the Green News on July 28th, 2017.

Legislation needed to protect European soil, new EU study finds

A new report published by the European Parliament’s committee responsible for scrutinising the European Commission’s agricultural policies has highlighted the threats facing soils across Europe.

The report – prepared by academic experts from Wageningen University, Aarhus University and the University of Cordoba – was presented to the European Parliament on 20th June and included a number of policy recommendations.

The experts emphasise the needs to reframe how we think about soil preservation to include the protection of ecosystem services provided by soils. These services include the provision of harvestable crops, clean fresh water and nutrients for plants and animals, conservation of biodiversity and maintenance of a stable climate.

Soils and soil ecosystem services in Europe are faced with numerous threats that limit their capacity to function and prospects to sustain into the future. Intensification of agriculture, urbanisation and land grabbing, and poor management practices have led to widespread reduction in soil fertility, nutrient content and biodiversity.

We are also seeing widespread destruction of soil due to erosion, compaction, salinisation and desertification.

Protection of organic-rich soils a priority

One of the primary threats identified in the report is the loss of soils with high organic carbon content. EU soils contain more than 70,000 million tonnes of carbon, dwarfing the 2,000 million tonnes of carbon emitted each year by Member States.

If we were to allow the release of even a fraction of this soil carbon to the atmosphere, we would easily undo all emissions reduction measures in other sectors.

Peatlands are the most efficient store of carbon in terrestrial ecosystems and Northern European peatlands represent almost 4 per cent of this global carbon reservoir.

Peatlands not only lock away carbon that will otherwise be emitted to the atmosphere but pristine peatlands also sequester 350 million tonnes of CO2 per year globally.

Many European peatlands have been degraded by drainage activities and associated spread of agriculture and other industries.

Agro-foresty and silvopastoral systems are highly productive agricultural lands and also have high carbon content. The loss of productive agricultural land to urbanisation and land sealing – trapping of soil beneath asphalt and concrete – is a major threat to these areas.

Given the projected substantial increases in global food demand, pressures on biodiversity and our continued commitment to reducing COemissions, the report states that we must preserve our most productive and carbon-rich soils.

Topsoil being washed away, subsoil under pressure

Twenty-two per cent of European land is affected by erosion from water and wind, a large proportion of which is directly related to conventional tillage activities. Transitioning to the use of no-tillage or minimal tillage practices would reduce the erosion of topsoil.

The increased use of catch crops and cover crops instead of traditional bare fallow approaches would also help reduce erosion. Over time, there would be the added benefit of increased nutrient, organic and water content of soils.

Policy measures that enforce adaption to these farming practices will be needed. The report also proposes the potential establishment of formal vulnerable zones.

About one-third of European soils, specifically the subsoil lying underneath topsoil, are badly impacted by compaction caused by heavy machinery. The continual pressure to increase labour productivity is driving this increased mechanization of agriculture.

The report calls for statutory maximum permissible limits to the wheel load carrying capacity for traffic on agricultural soils.

Moving towards agroecological practices

This reports adds to previously published research to conclude that we need to transition from conventional soil management practices to ecologically informed practices that improve soil quality. These include conservation agriculture and organic farming.

While many of the threats to soil traverse political borders, soil is undoubtedly more challenging to manage than water or air. This is due to the substantial geographic variation in soil parent material, climate, topography and historical management and usage.

The diverse nature of soil type and land usage across Europe necessitates that any policies must rank and implement measures based on local requirements.

The AGRI report recommends a ‘two-pronged’ approach – promotion and enforcement of local suitable practices at the farm level and the monitoring and evaluation at the catchment scale to test impacts of measures on ecosystem services.

The time for awareness and voluntary action has passed, the time for legislation long overdue

The AGRI report found – based on a survey of thousands of European farmers – that there is generally a high level of awareness among farmers about the importance of soils and the need for their protection.

The timescale of the proposed ‘no net land-take’ by 2050 – a target put forward in the Roadmap to a Resource Efficient Europe (COM 571/2011) – was also called into question. It is simply too long given the scale of the threat facing soils across Europe.

The EU Seventh Environment Action Programme states that sustainable soil management, soil protection and remediation of contaminated sites should be underway by 2020.

The EU has also signed up for the Sustainable Development Goals, which include elements of sustainable agriculture and soil protection. However, none of these initiatives includes legally binding provisions.

The People4Soil campaign is a European Citizen’s Initiative calling on the Commission to provide for such a legally binding framework.

The ECI is the EU’s direct democracy platform, enabling citizens to participate in the development of EU polices by petitioning the European Commission to make a legislative proposal.

If a petition receives one million signatures from European citizens from a least 7 out of the 28 Member States , within one year, the Commission is obliged to meet with the organisers and hold a public hearing on the proposals before deciding whether or not to propose new legislation on the issue.

People4Soil is supported by more than 500 organisations across Europe and needs its 1 million signatures by September 2017. Please sign the petition by following this link and you can do your part to help protect soils across Europe.

A version of this article appears in the Green News on June 22nd, 2017.