The year 2015 carries many titles. For physics fans, it is the International Year of Light, marking 100 years since Albert Einstein developed his general theory of relativity. For development experts, it is the International Year of Evaluation, a time to promote evidence-based policy-making.

But 2015 also bears earthier significance. The Food and Agriculture Organization of the United Nations (FAO) has decreed it the International Year of Soils. Britain’s leading Earth-sciences organization, the Geological Society in London, has also proclaimed it the Year of Mud. Just add rain. And, as visitors to Nature’s national and spiritual home can very often attest, what is soil to the world is mud in Britain.

Wet or dry, such dirty pursuits offer an important opportunity to highlight an oft-forgotten corner of the research world. Mud and soil science underlie many of the questions facing our planet, from how to feed billions of people to how to keep them safe from floods, fires and other natural disasters. Nature has long argued that researchers must be on the front lines of turning soil discoveries into practical advances. In 2012, one of our journalists travelled to Malawi to analyse the best ways to enrich African soil (see Nature 483, 525–527; 2012). Last week, we assessed the often-overhyped promise of biochar, burnt agricultural material meant to improve the performance of soils that it is mixed into (see Nature 517, 258–260; 2015).

The goal of the Year of Soils is to make others aware as well, and it offers a chance to marshal research initiatives to answer some of the most pressing questions. For instance, the FAO is focusing on updating and revising soil maps around the globe. ‘Legacy’ maps from Afghanistan to Zimbabwe have been scanned and made available online, providing key historical data for understanding how land use has changed over time. Looking ahead, an international consortium is working on producing a digital global soil map, georeferenced down to 100 metres.

Figuring out which soils lie where is just the first step; after that comes saving the best of what is left. The FAO estimates that an area of soil the size of Costa Rica is lost every year to factors such as erosion, compaction and salinization. One-third of the world’s soils have already been degraded, often in the countries that can least afford to lose that resource. When soil becomes sicker, so too do the people who rely on it. Contamination soars and crop yields and human health decline.

Somehow, researchers must also figure out a way for farmers to feed ever-increasing populations on ever-shrinking amounts of arable land. The solutions must take cost into account, because what works in the lab will not work in the field if the soil-treatment or conservation approach is too expensive for the people who need it most.

“When soil becomes sicker, so too do the people who rely on it.”

Against such enormous societal problems, the Geological Society’s decision to focus on mud might at first elicit a snigger: mud is a problem to face with wellies, not with a global research agenda. But take a moment to consider how mud influences the world of science.

For starters, there is the entire record of the history of life. Fossils preserved in mudstone, such as the exquisite Burgess Shale high in the Canadian Rockies, reveal the story of vertebrate evolution. Without small creatures drowning in and being encased by mud, we would have a much harder time unravelling the relationship between organisms past and present.

Then there is the economic importance of mud-based rocks. Petroleum engineers have been exploring shale as a future source of both oil and natural gas. Although controversy rages about how much shale gas might ultimately be available (see Nature 516, 28–30; 2014), extraction rates have soared in the United States, driven by big reserves such as the Marcellus Shale underlying much of Pennsylvania and neighbouring states. In March, industry and academic experts will gather in London to assess the numbers behind a possible ramp-up in shale-resource production in the United Kingdom.

Finally, consider how soil and mud combine to underpin many of the globe’s natural disasters. Assessing flood risk requires knowing what soils are where, and how likely they are to turn to mud in times of heavy downpours.

Now is the time to drill down hard on the big questions for soil science. Not all annual focuses are as relevant for society: 2016 has already been designated the International Year of Camelids.