Enhancing urban resilience through nature-based solutions

By Luiza Toledo, IIASA Science Communication Fellow 2019

2019 YSSP participant Regina Buono investigates how the law can support or impede the use of nature-based solutions and help facilitate adaptation to climate change.

Recognizing the need for a systemic change is the first step to overcoming environmental challenges like climate change. In theory, governance systems can be designed and arranged to facilitate and embrace adaptation to climate change. Developing a legal framework that supports such an adaptation is, however, a big challenge. Learning how to manage the environmental crisis we currently find ourselves in while still being able to grow economically further complicates matters. According to Regina Buono, a participant in this year’s IIASA Young Scientist Summer Program (YSSP), nature-based solutions could be an alternative option that offers a multitude of benefits in terms of how this dual goal of economic growth and sustainability can be achieved. Buono’s research will contribute to IIASA as a partner in the EU Horizon 2020 project, PHUSICOS, which is demonstrating how nature-based solutions can reduce the risk of extreme weather events in rural mountain landscapes.

Outdoor green living wall, vertical garden on modern office building | © Josefkubes | Dreamstime.com

Nature-based solutions are actions to protect, manage, or restore natural ecosystems that address societal challenges, such as water security, pollution, or natural disasters – sometimes simultaneously. These solutions take advantage of the system processes found in nature – such as the water regulation function of wetlands, the allowance of natural space in floodplains to buffer flooding impacts, water storage in recharged aquifers, or carbon storage in prairies – to tackle environmental problems. This concept is now widely used to reframe policy debates on biodiversity conservation, climate change adaptation and mitigation strategies, urban resilience, as well as the sustainable use of natural resources.

As part of her research, Buono is exploring how the law can support or impede the use of nature-based solutions and considering how we can make legal systems more adaptive so they can help facilitate societal adaptation to a more uncertain world under ongoing and future climate change.

“My research is about using the law as a tool that works for us, rather than one that, because of its historic interest in stability, gets in the way,” she says.

Regina Buono, YSSP participant. | © Buono

Buono started her career as a lawyer based in the US. In her first job she was assigned to work with water issues and according to her, it was “love at first sight”. Following that first assignment, she continued to work on finding market-based solutions for issues related to endangered species. She decided to pursue a PhD in public policy in 2016, and soon after was asked to join the external advisory board to the Nature Insurance Value: Assessment and Demonstration (NAIAD) project in Europe. While attending the first meeting, she realized that there were no lawyers or legal scholars among the project researchers. As a lawyer, she could see that there was a gap in understanding how law and regulations would impact the uptake, development, and proliferation of nature-based solutions.

Working with NAIAD, she developed her PhD dissertation to address this gap and advance understanding around the role of the law in nature-based solutions, both in terms of governance in implementation and practice and the potential for governance innovation that better supports and promotes future adaptation.

“My YSSP project here at IIASA focuses on the city of Valladolid, Spain, and examines the legal context around the implementation of a collection of nature-based solution projects. I am trying to draw insights from these that could perhaps also be applied to other cases,” she explains.

Buono is doing a critical qualitative study that integrates analyses of interviews and policy documents using NVivo, a qualitative data analysis computer software package specifically designed to work with very rich text-based and/or multimedia information, together with legal analysis. She says that there is still a lot of work to be done to adapt to climate change and an interdisciplinary cross-sector effort will be necessary.

The preliminary results from her YSSP research point to a number of constraints and facilitating factors related to law and regulation. She says that the lack of explicit legal authorization for nature-based solutions that she identified in her study, strict water quality regulations, and bureaucratic hurdles could be some of the factors that constrain the implementation of nature-based solutions. However, flexibility in the law and a polycentric governance structure was identified as facilitating factors that encourage local entities to opt for nature-based solutions.

Buono hopes that her research will help decision makers to assess and address legal components that guide, structure, or impede the use of nature-based solutions, and to consider how the law could be evolved to create a more enabling environment for more adaptive governance arrangements that would better support nature-based solutions.

“Our policies and infrastructure are going to have to change to be able to deal with the impacts that we are already experiencing. Nature-based solutions and a shift toward adaptive governance could help us navigate more gracefully in these important transitions,” she concludes.

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.

When breathing is expensive

By Luiza Toledo, IIASA Science Communication Fellow 2019

2019 YSSP participant Muye Ru investigates the main health impacts of air pollution and what this means for the economy and social development of a country.

© Sabelskaya | Dreamstime.com

Air pollution is one of the greatest environmental health risks of our time. It is the second most common cause of non-communicable diseases like stroke, cancer, and heart disease, and it annually leads to around seven million premature deaths.

According to the World Health Organization (WHO), almost 90% of people worldwide breathe polluted air. Even though we can say that air pollution is impartial, affecting people regardless of gender, race, social class, or economic status, the burden of ill health caused by air pollution primarily affects middle and low-income cities and marginalized populations. The economic cost of air pollution and its impacts on health is known as non-market costs and includes the monetized welfare costs of mortality (premature deaths), and of the disutility of illness (pain and suffering).

Muye Ru, YSSP participant. © Ru

Muye Ru, a 2019 Young Scientist Summer Program (YSSP) participant, is studying the main health impacts of air pollution and what this means for the economy and social development of a country. Her project will establish a methodology based on meta-analysis, to estimate the economic costs of selected morbidity outcomes of exposure to air pollution in a population, and test its application at various geographical scales (national, regional, and global).

“The idea behind my work is that bad air quality causes a burden for societies. We know that many people will die or be disabled because of it, but we don’t have a very good understanding of exactly what the social and economic cost of that is,” explains Ru.

It is easy to grasp that the burden of sick and disabled people will affect the economy of a country. For example, imagine a scenario where a family member is diagnosed with lung cancer. The illness will most probably influence the entire family in terms of loss of income when the person is unable to work due to his/her illness, or reduced funds available for savings and necessities like food and utilities due to the cost of treatment.

Ru’s project specifically focuses on the rate and duration of air pollution related-diseases in populations. According to her, this rate is extremely important once you start studying the high economic losses and social disturbances caused by illness and healthcare expenditures.

“It’s about how people are disabled, the effect of this burden on their lives, as well as how these changes in their lives are impacting the economy,” she says.

Ru hopes that her work will be useful to policymakers in creating and applying policies to combat air pollution that will lead to multiple benefits for the economy, the environment, and human health. She wants her research to make people more aware of how they are contributing to air pollution and how the cost of it affects everyone’s lives.

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.

How the environment shapes the way we behave

By Luiza Toledo, IIASA Science Communication Fellow 2019

2019 YSSP participant Roope Kaaronen investigates how changes in the urban environment affect people’s behavior and whether they will find it easy to engage in sustainable behavior in different environments.

Technological and industrial advances in many sectors have made our lives easier, but they have also contributed to a less sustainable way of life. From the industrial revolution to the present day, CO2 emissions have increased by 40% and about 95% of this increase can be attributed to human actions. We can therefore say that our actions shape the environment we live in. But how does the environment we live in in turn shape our attitudes and behavior?

Apart from the vast amount of information available to us and an increasing awareness of more sustainable consumption, our society still has a growing carbon footprint, which means that attitudes around sustainability are not really translating into behavior. There is a gap between having environmental knowledge and environmental awareness, and displaying pro-environmental behavior. Apparently, the answer to translating attitudes into behavior could have more to do with design than awareness.

Roope Kaaronen, YSSP participant. © Kaaronen

Roope Kaaronen, a member of this year’s IIASA Young Scientists Summer Program (YSSP) cohort, has made it his goal to study behavior change and the adoption of sustainable habits. His project investigates how changes in the urban environment will affect people’s behavior and whether people will find it easy to engage in sustainable behavior in different environments. He is looking at how pro-environmental behavior patterns emerge from processes of social learning (such as teaching and imitation), habituation, and niche construction (a process where agents shape the environment they act in).

“I am particularly interested in how the physical environment shapes our behaviors, because people often assume that they have a pro-environmental attitude or values, and that this automatically translates into sustainable behavior. Research however shows that this is often not the case. So actually, the physical environment is more important in determining how we behave than we think,” he explains.

For instance, suppose that you would like to start recycling more but your city doesn’t have a proper selective waste collection system. Because the infrastructure needed to promote pro-environmental behavior is missing, this can lead to feelings of frustration and hopelessness, which could in turn cause people to give up on even trying to engage in the behaviors that could lead to more sustainable outcomes.

Kaaronen uses agent-based modeling in his research to model the cultural evolution of sustainable behavior patterns. The idea is to study how opportunities for action can have self-reinforcing effects on behavior. He included agents who move on a “landscape of affordances” in his model, and these agents are connected to each other in a social network. In this context, the term “agents” represents individuals or groups in society.

Social psychology describes pro-environmental behavior as conscious actions made by an individual to minimize the negative impact of human activities on the environment. For Kaaronen, this means that we can only achieve sustainable goals if we change our behaviors or habits very quickly.

“I think that it’s not realistic to expect that technology will solve all our problems. We will have to start behaving differently,” he says.

Unfortunately, people very often assume that individuals’ actions don’t have as much impact as collective actions, leading them to postpone their own pro-environmental behaviors. There have been a lot of discussion in the media around whether one person’s attitude could have an impact on the environment, in other words, should the focus be on each individual making changes in the way they live, or should the focus be on whole systems changing. To Kaaronen, these two approaches are connected.

“Systems emerge from individuals and their collective interactions. As we are social animals, our actions are inevitably copied and imitated by other people. This means that a person who has a lot of influence will have many people copying them. In other words, whenever we talk about private environmental behavior, such as recycling or using public transport rather than driving a car, we tend to think that this is just our personal behavior, but of course, our choices form part of a much bigger system,” says Kaaronen.

Woman helps clean the beach of garbage. © Freemanhan2011 | Dreamstime.com

We should be aware that we need politicians to make our pro-environmental choices as easy as possible. As individuals, we have responsibilities because we are part of the social system, but it is up to the political system to encourage this kind of behavior on a larger scale.

In 2007, the Danish government developed a strategy that prioritized bicycling as method of transport in Copenhagen. Since then, the city has seen a rapid increase in the number of people cycling, showing that affordance is important to promoting behavior change. Kaaronen’s model is able to reproduce patterns of behavior change, such as the case of Copenhagen.

“I think in terms of policy, what I am doing is quite applicable in urban design. What I am trying to show is that if we make sustainable behavior easy and lucrative, this can lead to long lasting and self-reinforcing effects on the emergence of sustainable cultures,” he comments.

The advent of social media has made it easy to influence people’s attitudes and behavior. The model that Kaaronen is using also illustrates how behavior change can spread through tightly knit social networks, and how social learning in networks can have self-reinforcing effects on behavior change. He says that we should use this tool to spread awareness about sustainable habits and initiate cultural evolution towards sustainable societies. In terms of behavior, living by example is very important, since it is necessary to show that living a sustainable life is both possible and enjoyable. Kaaronen himself lives this philosophy as he doesn’t drive and tries not to eat meat. He also stopped flying two years ago.

“I am just travelling on the ground right now. It is part of a campaign in the academic environment called #FlyingLess. Buses and trains can take you to interesting places, but it of course takes up a lot of time and I realize that not everyone can do this because they live in places that aren’t well connected.”

We are so used to unsustainable forms of behavior like constantly driving, flying, and consuming meat, but the world needs to realize that this way of living cannot last forever. It is unsustainable. Even though it may appear challenging to change our behavior, Kaaronen’s research offers hope to keep believing that it is possible to change our unsustainable behavior and achieve a sustainable society and environment.

“I think it is important to show that these things are actually possible. We can reach a tipping point towards sustainable systems if enough people just start practicing what they preach,” he concludes.

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.

 

Rescuing the world from drowning

By Julian Hunt, IIASA postdoc

Possible location where the barriers could be installed © Anna Krivitskaia | Dreamstime.com

Sea 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.

The 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, implemented.

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.

The 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:

  1. 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.
  2. During the winter, the barrier is assembled over the frozen ice cover.
  3. 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.

Figure 1. (a) Proposed location of the submerged barrier or dam, (b) submerged barrier characterizes, (c) submerged dam characterizes.

There 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.

This 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 level rise.

References:

  1. 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]
  2. 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
  3. Moore J, Gladstone R, Zwinger T, and Wolovick M (2018) Geoengineer polar glaciers to slow sea-level rise. Nature: https://go.nature.com/2GoPcGp
  4. 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

Identifying hotspots of land use cover change in Mexico

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.

Skyline of Mexico City © Shane Adams | Dreamstime.com

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.

Reference:

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.

Moisture matters! What’s the impact of water thresholds and soil characteristics?

by Rastislav Skalsky, Ecosystems Services and Management Program, International Institute for Applied Systems Analysis

Clay soil

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.

Figure 1

Figure 1

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.

Sandy soil

Sandy soil

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.

Loamy soil

Loamy soil

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.

This blog was originally published on https://medium.com/grow-observatory-blog/moisture-matters-a9e33dc880a1