Rising CO2 – It's not just about Global Warming

30 September 2015 - By: Sarah Blackford

Rising CO2 – It's not just about Global Warming

By Sarah Blackford

Doing science in the laboratory has its own rewards, but doing science that helps change the world, that inspires people and changes the way they think is even better. That was the central message of the SEB+ Science with Impact session at Prague 2015, where four speakers told us why their research really mattered. This included tackling big issues, pushing to change global policy and inspiring people to use their science to make a difference. As the session chair, Alun Anderson, put it, “this is where we go beyond the science to its impact”.

Jodie Rummer (ARC Centre of Excellence for Coral Reef Studies, James Cook University, Australia) reminded us that elevated carbon dioxide levels don’t just cause higher global temperatures but also ocean acidification, as thirty per cent of the CO2 released into the atmosphere each year is absorbed by the oceans. The problem is that we don’t know how this will affect marine creatures in the long term. At first sight, fish appear to be surprisingly good at coping with rising acidity and can recover from acute acidosis by compensatory mechanisms, such as accumulating bicarbonate ions. This may not be surprising, given that fish evolved at a time when CO2 levels in the atmosphere were quite a bit higher than today, explained Jodie.

So does this mean that we don’t need to worry about how they will cope? Apparently not – Jodie argues that focusing on mortality rates can miss the sub-lethal effects of exposure to chronically high CO2. “Acid-base compensation requires substantial energy, and there could be trade-offs further down the line” she said. Her studies on coral reef fish yield startling results: “Although fish living under high CO2 may be able to maintain their ‘athletic’ performance, their behaviour is consistently compromised, possibly because disrupted ion balances in the brain may affect key neurotransmitters”, she said.

Jodie argues that there is an urgent need for greater knowledge on the molecular and genetic mechanisms behind these effects if we are to understand the long-term impact of ocean acidification and whether these animals have the capacity to adapt.

Just how important it is to have that level of understanding if we are to influence global policy was made clear by Hans-O. Pörtner (Alfred-Wegener Institute, Germany). Hans has spent years working as a coordinating lead author for the IPCC 5th Assessment Report, being responsible for the new chapter on “Ocean Systems” and also involved in the IPCC’s Synthesis Report and the Structured Expert Dialogue with UNFCCC. IPCC has the role of “influencing policy without being policy prescriptive”, as he puts it. It was astonishing to learn of the amount of time and effort involved in producing each of the report’s chapters before they are published. During each of the 3 rounds of reviews, each chapter can attract over 1,000 comments from the scientific community and government delegates, which the 7-8 authors of each chapter have to answer individually. The final about 5,000 page report is eventually condensed into a synthesis report and various summaries for policy makers, with a hope that this information will be used to direct human adaptation and climate mitigation strategies most effectively.

The latest report predicts some grim scenarios, especially for our oceans. “We are well on track to change ocean ecosystems", Hans said. “For instance, we are now projecting large scale losses of coral reef and Arctic sea ice ecosystems as well as species encounters that have not happened before and a shift in ocean productivity to the higher latitudes”. Combined with ocean acidification, the current models project that marine species are even more vulnerable than previously thought. But how does one convince policy makers to take action? According to Hans, the best strategy is to put the findings into a social and economic context: “As an example, the predictions show that there is a high risk to low latitude fisheries, which are mostly artisanal enterprises that do not have a high capacity to adapt to change”. Policy makers need to adapt long-term targets and goals to take into account the latest scientific evidence. “The preferred maximum warming temperature should now be 1.5 degrees, rather than the current two-degree target”, Hans said. The difference may seem subtle but given the combined effects of global warming and acidification, a two-degree warming would already take us into a high risk situation, he warns.

Naturally, policy makers want to hear about technologies that might make a transition to a lower carbon world easier. Alison Smith (University of Cambridge) is excited about the potential for algae to capture carbon for energy. Algae have many advantages over traditional biofuels: they do not compete for land space with food crops, their entire biomass can be used and their productivity rates outstrip land crops by 5-20 times. “Meeting the current UK diesel use would require 17.5 million hectares of oilseed rape but only 0.8 million hectares of algae”, Alison said. So why aren’t we already doing it? According to Alison, “the real problem is the cost – we currently cannot produce algal biomass at the scale possible to make it commercially viable".

Besides this, intensive algal farming may not be sustainable when all energy inputs are taken into account. Photobioreactors are energy hungry and need to be constantly supplied with light, carbon dioxide and nutrients. This means that the overall energy ratio (the amount of energy produced divided by the energy inputs) is negative. “Using photosynthetic organisms doesn’t automatically make it sustainable – you have to do the maths”, explained Alison.

But a little imagination could overcome some of these problems. For instance, coupling algae production to fixed installations that otherwise release carbon dioxide would create a ‘win-win’ situation. Running costs could also be offset by harvesting high value algal products such as astaxanthin, used by fish farms to dye salmon pink. “Solutions don’t have to be sophisticated – they can be really simple”, said Alison, giving an example from Africa. Here, plastic bags filled with algae are grown on waste left over from anaerobic digesters, proving that, although in its infancy, there is hope yet for an ‘algae-agronomy’. Perhaps one day every flat roof will boast its own algae-farm, busily turning sunshine into fuel…

“The challenge for scientists is to use our understanding of plants to help farmers to get more crop per drop”, said Bill Davies (Lancaster Environment Centre, Lancaster University), who concluded the session by highlighting the challenges that global warming will have on an already water-stressed world. “Unless we introduce new techniques in agriculture pretty quickly we’re not going to have enough water to produce the food we need", he said. There is particular concern for areas that experience high levels of tropospheric ozone, as this seems to make crops less able to regulate water loss. It is thought that ozone causes plants to produce more of the plant growth regulator ethylene which inhibits the action of abscisic acid (ABA), the plant hormone which regulates adaptive responses to drought.

One approach has been “partial root zone drying”. This smart technique uses the same amount of water as in conventional systems, but half of the root system is kept dry at any given time whilst the rest is irrigated. This causes ABA levels to change so that water-use efficiency increases without compromising crop yields. Farmers in the Gansu province of China are already benefiting from these techniques. This formerly productive area has gradually been turning to desert due to unsustainable water management practices. “A group of exceptionally bright PhD students took these ideas of deficit irrigation and hormone exploitation and made it work as simple, low-tech technologies”, Bill said. Now thousands of farmers use these techniques and, for the first time in sixty years, there is water in the Zhang River. “In summary” said Bill “my take-home message would be this: postgraduate students CAN and HAVE changed the world!”


For more information about the 111 project in Gansu province, see the article “Hope for a water scarce future” in the October 2014 SEB Bulletin. 

Category: Plant Biology
Sarah Blackford

Sarah Blackford

Sarah Blackford is the Head of Education and Public Affairs at the SEB and the editor of the SEB magazine. As a qualified careers adviser and MBTI practitioner, Sarah provides career development and support for SEB members and the wider scientific community. Sarah is also an active member within SEB+, focusing on a number of initiatives aimed at improving gender equality and diversity in the science field.