Fire ants dig tunnels efficiently by only a small percentage of the group doing most of the work. Free-loaders just sit around while their hard-working colleagues get things done. But might freeloaders actually be necessary for society to function efficiently? The answer could be yes.

Fire ants are highly social organisms. So, Goldman, a physicist at Georgia Tech, and his colleagues wanted to know how individual ants knew what to do without a central leader issuing orders. To find out, Goldman's team labeled individual fire ants with paint and then watched them dig their narrow tunnels —barely wide enough for two workers. Turns out, just 30 percent of the ants did 70 percent of the labor. “I was surprised that we ended up with so few workers actually doing the work at any one time.” A quarter of the ants never even entered the tunnel. Others crawled inside, but left without digging single grain of dirt. These idling behaviors ensured the tunnels did not get clogged with insect traffic, which would make the construction process stop.

And when the scientists removed the five hardest working ants from the colony, others immediately jumped in to compensate (补偿) — with no reduction in the group’s productivity. It seems that it doesn’t matter which ants are working or freeloading at a given time, as long as there is some division of labor to keep the tunnels flowing smoothly. The findings are in the journal Science.

The study could have implications for robotics. Imagine groups of robots sent to search rubble (碎石) for disaster survivors. Or nanobots (纳米机器人) coursing through our bodies to diagnose illness and deliver targeted medical treatment. Such robot groups will need to avoid getting jammed up in tight spaces. It might be necessary to program them so some just sit back and watch their comrades work.

The past few years have seen various tropical storms hit the coastlines of many countries throughout the world. Once they were considered a once-in-a-lifetime event but experts now think happenings of this nature will become more frequent because of the effects of climate change.

Particular attention is given by the Dutch to water management solutions, as more than 26% of the country is located under sea level. One of their most impressive achievements has been the reduction of their coastline by 700 km. During the 1950s, a series of projects in the southwest Netherlands called the Delta Works started to prevent the North Sea from entering the land. The structure is made up of six dams and four storm surge (风暴潮) barriers, which makes it the Netherlands largest flood defense.

Maeslantkering, another Delta Works project, is a storm surge barrier that protects the City of Rotterdam from floods. Completed in 1997, it is made up of two 6,800-ton gates that close under the control of a set of computers protecting people living in Rotterdam.

Another example is the green rooftops across the Netherlands, changing impermeable (不渗水的) surfaces into water-observant platforms during heavy rainfall. The benefits of green rooftops go beyond water management, as green roofs absorb summer heat during hot days, keeping structures inside cooler than they would otherwise be.

The Netherlands’ approach to reducing the effects of the new climate is also shaping the city’s landscape. Take watersquares for example. These are public spaces that serve as water containers during heavy rainfalls, preventing the flooding of the nearby streets while serving as gathering spots for the community during dry seasons. Since 2013, citizens of Rotterdam have been able to enjoy themselves in the first ever-built watersquare, which can hold about 1.7 million liters of water when needed.

The creative solutions being used in the Netherlands not only benefit the Dutch but also the rest of the world. As their water management solutions continue to be proven effective, other countries will be encouraged to carry out similar projects.

When we think about endangered species, we typically think of mammals such as whales, tigers or pandas. But the over 5, 500 of mammal species on Earth is a relatively poor number—and it pales in comparison with bacteria, of which there are at least a million different species.

Despite their vast numbers, little research has been done to understand the impact that modern human practices have on these tiny organisms（生物）, which have an important influence on many aspects of our lives.

There are also reasons for concern over the way humans are affecting bacterial species, and in many cases we are causing the same type of problems that affect larger organisms. Bacterial population structures are definitely changing, and bacterial species are being transported to new locations. Perhaps some bacteria are even on their way to extinction, although we don’t really have enough information to be certain yet.

Why should we care if bacteria are being spread to new places? Besides the obvious potential for spreading diseases to humans, animals and crops, there are also hidden dangers.

Microorganisms are invisible to the naked eye, so we tend to ignore them and don’t necessarily appreciate their role in how the planet operates. Bacteria are very important to biogeochemistry—the cycling of nutrition and other chemicals through ecosystems. For instance, before humans invented a way to make fertilizer industrially, every single nitrogen（氮）atom in our proteins and DNA had to be chemically caught by a bacterial cell before it could be taken in by plants and then enter the human food chain. The oxygen we breathe is largely made by microorganisms in the oceans rather than mainly by rainforests, as is opposite to common belief.

Our effects on bacteria have the potential to change these basic bacterial functions. It is vital to gain a better understanding of how humans are affecting microorganisms’ distribution, their abundance, and their life-keeping processes. Although bacteria are invisible, we overlook them at our own risk.