GeoLog

land use

Testing triggers of catastrophic climate change

Tipping points that could trigger catastrophic climate change via Wikimedia Commons.

Tipping points that could trigger catastrophic climate change via Wikimedia Commons.


The research presented during the EGU’s 2016 General Assembly have wide-reaching implications for how we understand planet Earth. In today’s post, Sara Mynott, an EGU press assistant during the conference, writes about findings presented at the meeting which highlight the importance of the biosphere when it comes to understanding the threat posed to our planet by environmental challenges.

With the climate changing, land use shifting and continued environmental pollution, something’s got to give. And if it does, it may well trigger catastrophic change. With so many threats to our planet’s integrity, making decisions about what environmental challenges we should tackle first is a challenge. This is why the Stockholm Resilience Centre created the planetary boundaries framework. The framework identifies key tipping points that could cause catastrophic climate change. Recent updates to the framework have identified biosphere integrity and climate change as two of the core planetary boundaries that, if crossed, could endanger human prosperity.

A lot of research has been done into the tipping points that could trigger catastrophic climate change, from large scale methane release to irreversible ice sheet melt, but one area remains profoundly overlooked. The biosphere.

“It’s very well known that the climate affects the biosphere and the biosphere affects the climate, but there’s still a large amount of uncertainty about how those two are going to interact and play out,” explains Steven Lade, a modeller at the Stockholm Resilience Centre.

Climate talks tend to focus around cutting CO2, but there is three times as much carbon stored in soils and vegetation than there is in the atmosphere, making the biosphere a major reservoir. By modelling interactions between the climate and the biosphere, Lade aims to find out whether biosphere degradation could trigger catastrophic climate change.

“There’s definitely enough carbon in the biosphere to cause catastrophic climate change. There’s no question about that. The question is how accessible it is, how rapidly it will be pumped out, how rapidly other feedbacks in the climate system might counteract that. The quantity is enough, but the speed and the feedbacks may help counteract that. This is why we’re trying to do a dynamical model.”

Just one small part of the biosphere. Credit: Paul via Wikimedia Commons.

Just one small part of the biosphere. Credit: Paul
via Wikimedia Commons.

Rather than predicting where these boundaries lie, Lade is looking for things that could cause catastrophic feedbacks. This means his models are relatively simple – a way of finding out what happens when you push life to its limits.  

“The point is to incorporate different assumptions about what people know, for example, about how the climate and biosphere interact and look at the consequences of those assumptions. To show, for example, whether the biosphere might be strong enough…if you stopped emitting more carbon, but degrade the biosphere heavily – could the resulting carbon emissions trigger catastrophic climate change?”

He aims to see whether those outcomes are plausible or not. It’s an interesting approach, one that will help shape decisions about we can prevent catastrophic change and let policy be put into practice.

By Sara Mynott

Sara is a science writer and marine science PhD candidate from the University of Exeter. She’s investigating the impact of climate change on predator-prey relationships in the ocean, and was one of our Press Assistants this year’s General Assembly.

 

GeoTalk: Veerle Vanacker on land use, degredation and the potential of revegitation

Today in GeoTalk, we’re talking to Veerle Vanacker, and eminent geomorphologist and winner of the EGU Division Outstanding Young Scientist Award last year. She tells us about her breakthroughs in modelling land use change and erosional processes…

First, could you introduce yourself and tell us a little about what you are currently working on?

I currently work as a lecturer in geomorphology at the University of Louvain (UCL, Belgium). My research focuses on the interactions between human activities and earth surface processes. After graduating from university (KULeuven, Belgium) in 1998, I started to conduct fieldwork in the Ecuadorian Andes in the scope of an inter-university cooperation project. My PhD research aimed to improve our understanding of the impact of land use change on geomorphic processes in tropical mountain environments. Remote sensing was then increasingly used to extract physical land properties. In 2002, I started as a post-doc with Eric Lambin, who chaired the IGBP Land Use Land Cover Change project at the time. Later, I relocated to the University of Hannover (Germany) to learn about new geochemical tracers to track erosion and sedimentation rates.

Veerle Vanaker out in the field (literally!). (Credit: Veerle Vanaker)

Veerle Vanaker out in the field (literally!). (Credit: Veerle Vanaker)

Last year, you received a Division Outstanding Young Scientists Awardfor your work on how land use change can influence erosion rates in mountainous regions. Could you tell us a bit more about your research in this area?

In mountainous regions, we commonly observe high erosion rates and elevated sediment fluxes. They are not directly a sign of increased human disturbances, as natural erosion rates in mountainous sites can be high due to steep slopes, tectonic activity, and the erosive climate. How to separate these processes from the impact of land use on sediment flux was a question that urgently needed answering. By combining spatial information (from remote sensing) with sediment flux data and geochemical tracers, we were able to quantify the changes in erosion rates due to anthropogenic disturbance.

The relationship between land use and erosion has been a subject of much debate, something your methods have helped resolve. Could you describe their key points?

Previous studies mostly used a time series of river sediment fluxes to analyse how erosion and sediment yield varied over time and space, but modern sediment fluxes don’t provide a good baseline for assessing human impacts on sediment flux as they are biased by both short records and long-term human occupation. Instead, we need natural benchmarks that we can compare disturbed areas to. In our studies, we established natural rates of sediment flux by looking at the concentration of terrestrial cosmogenic nuclides in river sediments. The beryllium isotope, 10Be, allows long-term catchment-wide denudational flux to be quantified. Modern sediment fluxes can then be compared to these rates to assess the impact of anthropogenic disturbance.

Vegetation on a degrated slope. Vegetation is a major control of runoff, erosion and sediment mobilization in highly degraded catchments. (Credit: Veerle Vanaker)

Vegetation on a degrated slope. Vegetation is a major control of runoff, erosion and sediment mobilization in highly degraded catchments. (Credit: Veerle Vanaker)

What activities have the greatest influence on sediment production and how can we reduce their impact?

Our studies showed that the conversion from native forests to agricultural land causes soil erosion to accelerate by up to two orders of magnitude. The main driver for this is the decrease in the protective ground vegetation cover. Such a loss of land cover can trigger shallow landslides, which present a major threat to human life, property and infrastructure.

Through our work in experimental catchments in the Andes, we were able to show that revegetation programs coupled with bioengineering significantly reduces sediment production and mobilisation. Revegetating active gully channels is a particularly efficient way of enhancing sediment trapping and infiltration of runoff water in gully channels, rather than transporting it downslope.

Lastly, what are your research plans for the future?

Human pressure on the land is globally increasing, which poses a serious threat to environmental sustainability. I’m highly interested in the interactions between soil systems and water, and what will happen to sediment and nutrient fluxes under changing human pressure. We observe that soil processes play a major role in the resilience of an ecosystem to human disturbance. To understand these interactions, we need new data on the rates of soil formation, chemical weathering and erosion fluxes for both undisturbed and anthropogenically disturbed sites. By combining data from different geochemical techniques, such as terrestrial and meteoric cosmogenic nuclides, with remote sensing data from very high resolution images, we should be able to make major advances in these research topics.

If you’d like to suggest a scientist for an interview, please contact Sara Mynott.