level rise is one of the most challenging impacts of climate change. The
continued rise in sea levels, partially caused by the melting of the ice sheets
of Greenland and Antarctica, will result in large scale impacts in coastal
areas as they are submerged by the sea. Locations not able to bear the costs of
implementing protection and adaptation measures will have to be abandoned,
resulting in social, economic and environmental losses.
most important mitigation goal for sea level rise is to reduce or possibly
revert carbon dioxide (CO2) emissions. Given the time lag between
emission reductions and the impacts of climate change, new adaptation measures
to reduce sea level rise should be proposed, developed and if possible,
A proposal that I developed during my D.Phil degree ten years ago, which resulted in a paper on the Mitigation and Adaptation to Global Change Journal1, shows that submerged barriers in front of ice sheets and glaciers would contribute to reducing the ice melt in Greenland. Edward Byers and I propose the construction of ten barriers at key glaciers in Greenland to stop the flow of warm salty ocean water reaching glaciers in Greenland and Atlantic, which are the main contributors to ice melting. This could reduce sea level rise by up to 5.3 meters at a levelized cost of US$275 million a year. The cost of the barriers is only a fraction of the estimated costs of adaptation measures to sea level rise around the world estimated to be US$1.4 trillion a year by 21002.
barrier consists of several plain sheet modules of marine grade steel around
200 mm thick connected to cylindrical steel tubes with air inside to keep the
barrier floating. The depth of the barriers varies from 30 – 500 meters and the
required length to stop the sea water from entering the fjords, where the
glaciers are located. As no such barrier has been developed before,
we propose three main
steps for the construction of the barrier:
The barrier components
should be transported to the designated location during the summer, when there
is no ocean ice cover and the access to the location of the barrier is less
challenging. Also during the summer, mooring structures should be added.
During the winter, the
barrier is assembled over the frozen ice cover.
During the next summer,
the ice cover will melt again and the barrier will float above the place where
it is should be fixed. The mooring chains attached to the barrier will pull the
barrier into place, using the mooring structures in the ground.
The concept of reducing the contact of seawater and glaciers to reduce ice sheet melting was first published by Moore in Nature3, and Wolovick in The Cryosphere4 with the construction of submerged dams. A graphic representation of the concept is presented in Figure 1. As you can see the barriers should be positioned just after the glacier cavity, where the depth required for the barrier would be the smallest. Our cost analysis shows that using submerged barriers would have one or two orders of magnitude lower costs when compared to submerged dams. Additionally, submerged barriers could be easily removed, if the need arise.
are several issues involving the implementation of these barriers that should
be considered before they are built. The reduction of ice melt in Greenland
glaciers will contribute to an increase in seawater temperature and salinity of
the Arctic Ocean, which will have a direct impact on the region’s biosphere,
climate and ocean currents. The superficial ice cover in the Arctic will be
considerably reduced. This would allow a new maritime route for ships to cross
the Arctic Ocean, increase the absorption of CO2 by the Arctic Ocean,
due to the increase in the ice free surface area and the cold seawater temperature,
and the increase in radiation heat from the Arctic Ocean into space. Ice is a
strong thermal insulator. Without the Arctic Ocean ice cover the temperature of
the region and the heat radiated from the Earth to space will considerably
increase, which could have a higher impact in cooling the Earth than the ice
cover’s albedo effect. Thus, the reduction of the Arctic Ocean ice cover could
contribute to reducing the overall CO2 concentration of the
atmosphere and reducing the Earth’s temperature.
solution, however, should not be used as an excuse to reduce focus on cutting
CO2 emission. If the world continues to warm, not even submerged
barriers in front of glaciers would be able to stop ice sheets melting and sea
Hunt J, Byers E (2018) Reducing sea level rise with submerged barriers and dams in Greenland. Mitigation and Adaptation Strategies for Global Change DOI: 10.1007/s11027-018-9831-y. [pure.iiasa.ac.at/15649]
Jevrejeva JS, Jackson LP, Grinsted A, Lincke D, and Marzeion B (2018) Flood damage costs under the sea level rise with warming of 1.5 ◦C and 2 ◦C. Environmental Research Letters DOI: 10.1088/1748-9326/aacc76
Moore J, Gladstone R, Zwinger T, and Wolovick M (2018) Geoengineer polar glaciers to slow sea-level rise. Nature: /
Wolovick M, Moore J (2018) Stopping the flood: could we use targeted geoengineering to mitigate sea level rise? The Cryosphere DOI: 10.5194/tc-12-2955-2018
By Alma Mendoza, Colosio Fellow with the IIASA Ecosystems Services and Management Program
Changes in land use cover can have a crucial impact on the environment in terms of biodiversity and the benefits that ecosystems provide to people. Assessing, quantifying, and identifying where these changes are the most drastic is especially important in countries that have high biodiversity along with high rates of natural vegetation loss. Socioeconomic pressures often drive land use change and the impacts are expected to increase due to population growth and climate change.
To better understand the possible impacts of land use change in Mexico over the short, medium, and long term, my colleagues and I used the Shared Socioeconomic Pathways–a set of pathways that span a wide range of feasible future developments in areas such as agriculture, population, and the economy–together with a set of climatic scenarios known as the Representative Concentration Pathways. We focused on Mexico, because the country is large enough to encompass different ecosystems, socioeconomic characteristics, and climates. In addition, Mexico is characterized by high deforestation rates, huge biodiversity, and a large number of communities with contrasting land management practices. Incorporating all these features, allowed us to take the complexity of socioecological systems into account.
We designed a model to test how socioeconomic and biophysical drivers, like slope or altitude, may unfold under different scenarios and affect land use. Our model includes 13 categories of which eight represent the most important ecosystems in Mexico (temperate forests, cloud forests, mangroves, scrublands, tropical evergreen and -dry forests, natural grasslands, and other vegetation such as desert ecosystems or natural palms), four represent anthropogenic uses (pasture, rainfed and irrigated agriculture, and human settlements), and one constitutes barren lands. We set two plausible scenarios: “Business as usual” and an optimistic scenario called the “green scenario”. We projected the “business as usual” scenario using medium rates of vegetation loss based on historical trends and combined it with a medium population and economic growth with medium increases in climatic conditions. For the “green scenario”, we projected the lowest rates of native vegetation loss and the highest rates of native vegetation recovery with a low population and medium economic growth in a future with low climatic changes.
Our results show that natural vegetation will undergo significant reductions in Mexico and that different types of vegetation will be affected differently. Tropical dry and evergreen forests, followed by ‘other’ vegetation and cloud forests are the most vulnerable ecosystems in the country. For example, according to the “business as usual” scenario, tropical dry forests might decrease in extent by 47% by the end of the century. This is extremely important considering that the most recent rates, for the period 2007 to 2011, were even higher than the medium rates we used in this scenario. In contrast, the “green scenario” allowed us to see that, with feasible changes of rate, this ecosystem could increase their distribution. However, even 80 years of regeneration would not be enough to reach the extent these forests had in 1985, when they accounted for around 12% of land cover in Mexico. Moreover, the expansion of anthropogenic land cover (such as agriculture, pastures, and human settlements) might reach 37% of land cover in the country by 2050 and 43% by 2100 under the same scenario. In terms of CO2 emissions due to land use cover change we found that Mexico was responsible for 1-2% of global emissions that are the result of land use cover change, but by 2100 it could account for as much as 5%.
Our findings show that conservation policies have not been effective enough to avoid land use cover change, especially in tropical evergreen forests and drier ecosystems such as tropical dry forests, natural grasslands, and other vegetation. Cloud forests have also been badly affected. As a biologically and culturally rich country, Mexico is responsible for maintaining its diversity by implementing a sustainable and intelligent management of its territory.
Our study identified hotspots of land use change that can help to prioritize areas for improving environmental performance. Our project is currently linking the hotspots of change with the most threatened and endemic species of Mexican terrestrial vertebrates (mammals, amphibians, reptiles, and birds) to provide useful results that can help prioritize ecosystems, species, or municipalities in Mexico.
Mendoza Ponce A, Corona-Núñez R, Kraxner F, Leduc S, & Patrizio P (2018). Identifying effects of land use cover changes and climate change on terrestrial ecosystems and carbon stocks in Mexico. Global Environmental Change 53: 12-23. [pure.iiasa.ac.at/15462]
Note: This article gives the views of the author, and not the position of the Nexus blog, nor of the International Institute for Applied Systems Analysis.
by Rastislav Skalsky, Ecosystems Services and Management Program, International Institute for Applied Systems Analysis
As growers, we know soil is important. It supports plants, and provides nutrients and water for them to grow. But do we all appreciate how crucial the role of soil is in continuously supplying plants with water, even when it hasn’t rained for a few days or even weeks, even without extra water being added via watering?
Soil is like a sponge. It can retain rain water and, if it is not taken up by plants, soil can store it for a long time. We can feel the water in soil as soil moisture. Try it — take and hold a lump (clod) of soil — if it is wet it will leave a spot on your palm. If it’s only moist then it will feel cold — cooler than the air around. And if the soil is dry, it will feel a little warm.
Soil moisture not only can be felt, but it can also be measured — in the lab, or directly in the field with professional or low-cost soil moisture sensors.
Soil moisture in general indicates how much water is contained by the soil. But it is not always the case that soil which feels moist or wet is able to support plants. It could happen that, despite feeling moist, the soil simply does not hold enough water, or holds the water too tightly for the plants to extract it. Or the opposite, soil can sometimes contain too much water. To understand how this works, one has to learn more about how water is stored in the soil.
Water is bound to soil by physical forces. Some forces are too weak to hold water in the plant root zone and water percolates to deeper layers, where plants can no longer reach it. Other forces can be too strong, preventing water from being retrieved by the roots.
If soil moisture is measured at one place over time, it can reveal its seasonal dynamics. Having estimated important soil water content thresholds (FS — full saturation, FC — field capacity, PDA — point of decreased availability, and WP — wilting point) for that particular site, e.g. based on soil texture test or measurement, one can easily interpret if the measured soil moisture and say if there was enough water or not to fully support plants with water and air. In this particular case of sandy 0–30 cm deep topsoil from Slovakia, it was never wet enough to cause oxygen stress for plants, — in fact it never reached state of all capillary voids filled with water (FC). On the other hand, each summer the topsoil moisture dropped below the point of decreased availability (PDA), even got close to the wilting point or went through (WP), which means that during those periods plants suffered drought conditions.
Thresholds In order to describe this behavior in more useful terms, plant ecologists and soil hydrologists came up with couple of important soil water content thresholds (Figure 1). These thresholds, also called “soil moisture ecological intervals”, define how easily plants can get the water out of the soil.
We speak about full saturation of soil when all empty spaces (pores/voids) are completely filled with water. Full saturation of the soil with water prevents air entering into the soil. Yet there is no force holding water in the soil. Roots need air as well as water so, if this situation continues, it eventually causes oxygen stress for most of the common plants because roots simply cannot breathe.
Soil also has different types of pores. Larger ones, which are called “gravitational pores”, are filled with water only when the soil is saturated and otherwise drains freely, and smaller ones called “capillary pores” which are small enough in size to prevent water from percolating down the soil profile by gravitation. These smaller pores can hold water even in well-drained soils and make it available for plants to extract. There are also even smaller pores where the water is held so tightly that plants cannot extract it.
When all gravitational pores/voids are empty of water and it is present only in so called capillary pores/void we speak about the field water capacity — which is considered to be the best soil moisture status of the soil — enabling plants to retrieve the water they need, whilst leaving enough air for roots to breathe. If no new water is added into the soil, the soil dries as water is used by plants or evaporates. As soil dries less water is available to plants until the point of decreased availability when water remains only in the smallest capillary pores/voids. But this water is bound to soil particles so strongly that most plants are not able to extract it suffer from drought. Ultimately, all the available water is used up by plants, and the remaining water is inaccessible. Soil reaches the so-called wilting point and water is not available for the plants anymore. Plants permanently wilt and eventually die.
How Soil Characteristics Relate to Moisture The tricky thing with soil moisture however is that the same amount of water (volumetric percent of the total soil column volume) can, in different soils, represent different amount of water available for plants. How big this difference could be is defined by many soil characteristics.
The most important is the soil texture — a blend of all fine-earth soil mineral constituents (sand, silt, clay) and stones in various rates. In general, the finer the texture is (i.e. more clay, less sand) the more water is bound in the soil too tightly to be retrieved by plants. Even if the soil feels moist, plants can permanently wilt in clay soils. In contrast, those soils with coarse texture (i.e. more sand, less clay) can support plants with nearly all the water they can hold. Although the soil looks dry, plants can still effectively take the water out of it. The drawback here is that in coarse textured, sandy, soil nearly all water drains down the gravitational pores and therefore such a soil cannot support plants for very long time. That is also why medium textured soils (loam, silty loam, clay loam) are considered best for holding and providing the water for plants. Medium textured soils can effectively drain excess water, yet hold much water in capillary pores/voids for a long time, and still, only a relatively small amount of water remains unavailable for the plants.
A practical implication of this behavior of soil with different soil texture could be that one has to apply slightly different strategies to maintain soil moisture in the way that it can effectively supply plants with water. Sandy soils will require more frequent watering with smaller amount of water. It would not make any practical sense to try build-up a storage of water in these soils. All extra water added will simply drain out of the topsoil. Clay rich soils can absorb big amounts of water but a lot is bounded too strongly to the soil particles and thus not available for the plants. Therefore one should water even if the soil looks moist or wet — and if dry a lot of water must be added to recharge the topsoil so that it can support plants effectively. With loamy soils it is possible to be more relaxed with watering frequency, simply because one can build solid storage of water in such soils. Adding a bit more water than is necessary is perfectly fine with these soils because the water is effectively kept in the soil profile and it can be used later on.
Interested in learning more? Why not sign up for GROW Observatory’s next free online course – Citizen Research: From Data to Action – to discover how citizen-generated data on soils, food and a changing climate can create positive change in the world. Starts 5th November.
On 14 and 15 May, Vienna hosted two important events within the frame of the world energy and climate change agendas: the Vienna Energy Forum and the R20 Austrian World Summit. Since I had the pleasure and privilege to attend both, I would like to share some insights and relevant messages I took home with me.
To begin with, ‘renewable energy’ was the buzzword of the moment. Renewable energy is not only the future, it is the present. Recently, 20-year solar PV contracts were signed for US$0.02/kWh. However, renewable energy is not only about mitigating the effects of climate change, but also about turning the planet into a world we (humans from all regions, regardless of the local conditions) want to live in. It is not only about producing energy, about reaching a number of KWh equivalent to the expected demand–renewables are about providing a service to communities, meeting their needs, and improving their ways of life. It does not consist only of taking a solar LED lamp to a remote rural house in India or Africa. It is about first understanding the problem and then seeking the right solution. Such a light will be of no use if a mother has to spend the whole day walking 10 km to find water at the closest spring or well, and come back by sunset to work on her loom, only to find that the lamp has run out of battery. Why? Because her son had to take it to school to light his way back home.
This is where the concept of ‘nexus’ entered the room, and I have to say that more than once it was brought up by IIASA Deputy Director General Nebojsa Nakicenovic. A nexus approach means adopting an integrated approach and understanding both the problems and the solutions, the cross and rebound effects, and the synergies; and it is on the latter that we should focus our efforts to maximize the effect with minimal effort. Looking at the nexus involves addressing the interdependencies between the water, energy, and food sectors, but also expanding the reach to other critical dimensions such as health, poverty, education, and gender. Overall, this means pursuing the Sustainable Development Goals (SDGs).
Another key word that was repeatedly mentioned was finance. The question was how to raise and mobilize funds for the implementation of the required solutions and initiatives. The answer: blended funding and private funding mobilization. This means combining different funding sources, including crowd funding and citizen-social funding initiatives, and engaging the private sector by reducing the risk for investors. A wonderful example was presented by the city of Vienna, where a solar power plant was completely funded (and thus owned) by Viennese citizens through the purchase of shares.
This connects with the last message: the importance of a bottom-up approach and the critical role of those at the local level. Speakers and panelists gave several examples of successful initiatives in Mali, India, Vienna, and California. Most of the debates focused on how to search for solutions and facilitate access to funding and implementation in the Global South. However, two things became clear. Firstly, massive political and investment efforts are required in emerging countries to set up the infrastructural and social environment (including capacity building) to achieve the SDGs. Secondly, the effort and cost of dismantling a well-rooted technological and infrastructural system once put in place, such as fossil fuel-based power networks in the case of developed countries, are also huge. Hence, the importance of emerging economies going directly for sustainable solutions, which will pay off in the future in all possible aspects. HRH Princess Abze Djigma from Burkina Faso emphasized that this is already happening in Africa. Progress is being made at a critical rate, triggered by local initiatives that will displace the age of huge, donor-funded, top-down projects, to give way to bottom-up, collaborative co-funding and co-development.
Overall, if I had to pick just one message among the information overload I faced over these two days, it would be the statement by a young fellow in the audience from African Champions: “Africa is not underdeveloped, it is waiting and watching not to repeat the mistakes made by the rest of the world.” We should keep this message in mind.
By Linda See and Inian Moorthy, Ecosystems Services and Management Program
A recent estimate indicates that there are around 3 trillion trees on the Earth’s surface, of which around 15 billion are cut down each year . When we think of these vast numbers, we usually picture Amazonian rainforests or landscapes of evergreen trees surrounded by lakes and mountains. We rarely think of urban trees and the important role they play in making cities a healthier, greener place to live.
Raising awareness of the importance of urban forests for quality of life is part of the theme of this year’s United Nations International Day of Forests. At IIASA we are actively contributing to this awareness through an EU-funded project called LandSense. The aim of the project is to create a citizen-powered observatory for environmental monitoring of landscapes, particularly those that are changing and affecting citizen wellbeing, livelihoods, and biodiversity. Monitoring trees, and more specifically urban greenspaces, is a fundamental component of the LandSense project. Trees can reduce air pollution in cities by absorbing and filtering out the gases and particles that cause harm. Additionally, trees have a cooling effect on cities, which is increasingly important as temperatures rise due to climate change. In cities, the urban heat island effect results in higher temperatures during heat waves, often leading to health problems and even fatalities. Monitoring the presence of urban trees and fostering citizen access to urban greenspaces should therefore not be underestimated in terms of their contribution to promoting urban health, wellbeing, and sustainable cities.
With this urban focus in mind, the LandSense citizen observatory is engaging citizens in Vienna and Amsterdam in monitoring their local greenspaces, and in this way obtaining their perceptions about the quality and extent of these areas. A smart phone app developed at IIASA, guides participating citizens to specific locations in the city and asks them a series of questions, some of which relate to the quality of the trees in their area. This feedback can help city authorities to better understand the views of their citizens. The ultimate goal is to create dynamic and temporal maps of greenspace quality across the city, which can guide timely local decision making. The LandSense app will for example, directly contribute to STEP 2025, the urban development plan for Vienna.
This participatory approach not only gives citizens a better understanding of changing greenspaces in the city, but also empowers them to elicit action from city authorities in terms of improving poorly perceived greenspaces. By participating in this process, citizens are actively engaging in dialogue with the city authorities – getting their voices heard and influencing where future improvements will take place. Ultimately, by improving greenspaces and urban forests, citizens are helping to increase the wellbeing and quality of life of urban dwellers in the city.
We are currently testing the mobile app with students in Vienna and Amsterdam before launching broader citizen-based greenspace monitoring campaigns in the future. If you want to find out more, please visit the LandSense website for details or follow us on Twitter @LandSense.
 Crowther TW, Glick HB, Covey KR, et al (2015). Mapping tree density at a global scale. Nature 525:201–205. doi: 10.1038/nature14967
Note: This article gives the views of the authors, and not the position of the Nexus blog, nor of the International Institute for Applied Systems Analysis.