World Soil Moisture

acquired May 27 - 31, 2015

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Look at natural-color satellite images and it becomes clear that most of the water on Earth (about 97 percent) is stored in the oceans. Next you might notice some on the land: liquid water fills lakes and rivers, while frozen water blankets the poles and mountaintops. In the atmosphere, water is visible in the countless tiny droplets that compose the clouds, though there is plenty of moisture even in cloud-free skies.

Not immediately visible, however, is the water residing in the soil. This water does not appear brilliantly blue or white, like the oceans or ice. In fact, it is hard to spot in natural-color satellite images.

Compared to the amount of water stored elsewhere on the planet, the amount in the soil is minuscule. But that small volume has great significance. It can affect when, where, and what a farmer will plant. It can influence the weather. And at high northern latitudes, soil moisture has serious implications for global climate.

For all of these reasons, researchers have developed satellite instruments to measure the water hidden between soil particles. The instruments are either active or passive. Active sensors allow scientists to measure moisture in very specific areas (high resolution), but they are less accurate than other sensors. In contrast, passive measurements give better estimates of the amount of water, but over a broader area (coarse spatial resolution) than active radar. NASA’s Soil Moisture Active Passive (SMAP) satellite was launched in January 2015 and carries both a radiometer and radar. (Note: the radar stopped transmitting data in July 2015.)

The map above was produced with data collected by SMAP’s radar and radiometer from May 27–31, 2015. It shows the amount of moisture in the top 5 centimeters of the ground at a resolution of about 9 kilometers. Data are mapped as the fraction of the volume of water contained in a volume of soil. Dark green and blue areas are progressively wetter, up to a ratio of about 0.5; at that point, the ground is considered saturated.

As expected, deserts around the world have low soil moisture content, and appear light yellow in this map. Soils in areas such as rainforests, boreal forests, and vegetated mountain regions are generally wetter.

There is often good correspondence between areas where meteorologists observe high amounts of rainfall and areas of maximum soil moisture, as was the case in October 2015 following extreme rainfall in the eastern United States. But soil moisture depends on other factors, too, such as the state of the soil preceding an event. Soil that is already wet can saturate more quickly and cause runoff and flooding.

Space-based platforms like SMAP, combined with insights from ground-based sensors, contribute to a growing record of global soil moisture. The goal is to establish a standardized set of measurements for the entire planet so that everyone from meteorologists to climate modelers can track the movement of this small but vital reservoir of water.

Read more in our latest feature story: A Little Bit of Water, A Lot of Impact.

Selected ReadingLu, H. et al., (2009) Monitoring Soil Moisture from Spaceborne Passive Microwave Radiometers: Algorithm Developments and Applications to AMSR-E and SSM/I. Advances in Geoscience and Remote Sensing, Chapter 17.
NASA’s Jet Propulsion Laboratory (2015) Soil Moisture Active Passive (SMAP).
NASA’s Jet Propulsion Laboratory (2015, March 9) NASA’s Soil Moisture Mapper Takes First ‘SMAPshots’. Accessed September 16, 2015.
SMAP Mission Brochure (2014) Mapping Soil Moisture and Freeze/Thaw State from Space. Accessed September 16, 2015.

NASA Earth Observatory map by Joshua Stevens, using data courtesy of JPL and the SMAP science team. Caption by Kathryn Hansen.

Instrument(s): SMAP

Source: Nasa Earth Observatory

6 Amazing Global Agriculture Maps – Farming Visualized

Agriculture Maps

Visualizing Farming with Agriculture Maps
Ever wonder where your food comes from? We have 6 agriculture maps to show you the answer.

Almost every bit of the food we eat is grown and gathered on farms. Humans have learned how to change the environment to most-effectively grow crops. We’ve also learned to produce more crops with less land. But a number of issues threatens agriculture sustainability – population increase, climate change and water stress.

Feast your eyes on these agriculture maps and learn what the future of farming holds.

1. Agricultural Exposure to Water Stress Map
Agriculture takes advantage of the nutrients in the soil and the amount of water that is available. Water is the key. When crops aren’t getting enough water, farmers have to find ways to bring water to the crops. This is called irrigation. Irrigation can change dry land into fertile farmland. To get water needed for crops, we build reservoirs and drill deep wells. Irrigation is a big part of farming.

The World Resources Institute has mapped out where these water stresses exist in the world. The Agriculture Exposure to Water Stress Map measures the ratio of local withdrawal (demand) over the available water (supply). Countries like India, Morocco, Spain and the Philippines face high cropland water stress.. Other major commodity crops are visualized like coffee, rice and cereals.

2. Feeding the World Map

Crop production will have to double by 2050 to fulfill the needs of a growing and increasingly affluent population. Meeting this challenge will be difficult but not impossible, according to the University of Minnesota’s Institute on the Environment

Can Global Crop Production Meet Future Demands? The University of Minnesota is exploring current crop yields and solutions to the biggest problems in agriculture. This is the purpose of the Feeding the World Story Map. In order to tackle this growing problem, we will have to:

• Make croplands more productive
• Increase water use efficiency
• Change crop use & diet

3. World Bank Agricultural Land (% of land area)

World Bank has a unique set of Agriculture Maps showing historical and future farming trends. Agriculture maps include:

• Agricultural irrigated land (% of total agricultural land)
• Agricultural land (% of land area)
• Agricultural machinery (tractors per 100 sq km of arable land)
• Agriculture, value added (% of GDP)
• Agriculture, value added per worker (constant 2005 US$)

4. Food and Agriculture Organization (FAO) of the United Nations Hunger Map

One in seven people on Earth live on less than one dollar each day
Hunger means going without an adequate meal for days. It prevents adults from working and stunts the growth of babies. It affects one out of nine people every day. The majority of hunger issues are in developing countries.

The United Nations is combating hunger with its Millennium Development Goal (MDG) program. The UN has set a target to halve in the developing world. The interactive UN Hunger Map raises awareness about global hunger.

5. ISRIC Soil Grids 1KM
Plants live in dirt. Rich topsoil is filled of living things like bugs, worms, roots and dead leaves. In the soil business, this is called organic material. Let’s say topsoil comprised of 10% organic material and the rest sand and rocks. The nutrients that plants take up in their roots comes from that 10% organic material. Without organic material, hardly any plants could grow. And it takes centuries for topsoil to grow.

But other factors come into play for crop production. Soil texture (sand %, silt % and clay %) is important because it influences nutrient retention. Cation exchange capacity indicates how the soil can supply nutrients like calcium, magnesium and potassium.

ISRIC’s 1km Global Soil Map helps with agriculture decision-making. Some of the greatest soil maps can be found with properties like taxonomy, organic carbon, pH in H2O, sand %, silt %, clay %, cation exchange capacity, bulk density and coarse fragments

6. FAO Global Spatial Database of Agricultural Land-use Statistics
Agro-maps breaks down primary food crops by sub-national administrative districts. The information is aggregated by crop production, area harvested and crop yields.

About 40% of the global workforce is in agriculture. That’s 1.3 billion people. This means that agriculture is the world’s largest provider of jobs. In the FAO Global Spatial Database and Agricultural Land-use Interactive Map, you get a limited yet very important component of land use.

Agriculture Maps for Decision Making
Agriculture feeds the globe. We can see which crop types are suited for different environments in this list of agriculture maps.

Farming also faces a number of problems – population increase, climate change, hunger and water stress. Agriculture maps can convey this information to make knowledgeable decisions.

Instantly, you have become more knowledgeable about agricultural issues with these 6 agriculture maps.

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