Earth’s longest artificial structure is usually said to be the Great Wall of China while the second-longest is not a wall, but a fence. It stretches for 5,614km across eastern Australia and is intended to stop the country’s wild dogs, the dingoes (野犬), from hunting sheep.

Australia’s dingo fence does not stand alone. Millions of kilometres of fences wrap the world.

Some are intended to limit the movement of animals, some the movement of people, and some merely to mark the boundary.

Until recently, data on the effects of fences on wildlife have been inadequate. That has changed with the publication of a report by Professor Alex Mclnturff. One discovery he has made is that more than half of published fence research focuses on just five countries — America, Australia, Botswana, China and South Africa. A second is that only a third of these studies examined the impact of fences on anything other than the target species involved, meaning the animals purposely intended to be kept in or out.

Non-target species, however, are often those that have their fortunes most greatly reshaped by the appearance of poles and wire. Australian fences intended to keep out dingoes are also barriers to long-necked turtles, which travel great distances over land when moving between nesting sites. In Botswana fences built to spare cattle from wildlife-borne disease result in serious interference with wildebeest (角马) migrations.

Not every creature fares badly. Hawks (鹰) in Montana gladly sit on newly built livestock fences to hunt small animals, while fence-based spiders in South Africa outperform their tree-based cousins when it comes to catching insects.

Often, though, the winners are creatures that cause trouble for existing ecosystems. Keeping dingoes out of large parts of Australia has allowed aggressive red foxes to multiply. Native rodents (啮齿类动物) have suffered as a result. Some have been brought to the edge of extinction.

The rainforests are alive with the sound of animals. Besides the pleasure of the din, it is also useful to ecologists. If you want to measure the biodiversity of a piece of land, listening out for animal calls is much easier than digging about in the undergrowth looking for tracks. But such “bio-acoustic analysis” is still time-consuming, and it requires an expert pair of ears.

In a paper published on October 17th in Nature Communications, a group of researchers led by Jörg Müller, an ecologist at the University of Würzburg, describe a better way: have a computer do the job. Smartphone apps already exist that will identify birds, bats or mammals simply by listening to the sounds they make. Their idea was to apply the principle to conservation work.

The researchers took recordings from across 43 sites in the Ecuadorean rainforest. Sound recordings were taken four times every hour, over two weeks. The various calls were identified manually by an expert, and then used to construct a list of the species present. As expected, the longer the land had been free from agricultural activity, the greater the biodiversity it hosted.

Then it was the computer’s turn. The researchers fed their recordings to artificial-intelligence models that had been trained, using sound samples from elsewhere in Ecuador, to identify 75 bird species from their calls. “We found that the AI tools could identify the sounds as well as the experts,” says Dr Müller.

Of course, not everything in a rainforest makes a noise. Dr Müller and his colleagues used light-traps to capture night-flying insects, and DNA analysis to identify them. Reassuringly, they found that the diversity of noisy animals was a reliable proxy (指标) for the diversity of the quieter ones, too.

The results may have relevance outside ecology departments, too. Under pressure from their customers, firms such as L’Oreal, a make-up company, and Shell, an oil firm, have been spending money on forest restoration projects around the world. Dr Müller hopes that an automated approach to checking on the results could help monitor such efforts, and give a standardized way to measure whether they are working as well as their sponsors say.

What is self-discipline? It’s the ability to make yourself do something, especially something difficult or unpleasant. When some people hear self-discipline, they think it’s boring. Before I get into my thoughts on the topic, I want to tell you a story.

On a hot sunny day, a bee named Bertha is buzzing by her hive with some other bees. Suddenly a bear starts to approach her hive. In an attempt to save her hive, Bertha stings (蜇) the bear. But its skin is so thick that once she tries to pull her sting out, she hurts herself and dies. Bertha has no choice. Through years of evolution (进化), she is evolved to sting threats, which is her born ability. She lacks thinking consciousness.

Bees are prisoners of their own biology. Unlike bees, humans have the ability to override (推翻) their biology through self-discipline. Let’s say that someone has long-term desires to create a meaningful career and have a healthy body. Along each step of that journey they are attracted by short-term pleasures, such as junk food or video games. Deep down they really want the life that comes in the long term. Yet they keep submitting to short-term pleasures. The only difference between these two positions is self-discipline. It gives us the freedom to achieve what we truly want in life and allows us to break free of the cages around us.

Video games imitate the environments similar to the ones that our ancestors navigated in the past, but have supernormal versions of them. We can get greater feelings of accomplishment in video games with a lot less work. Companies are aware that the constant achievements on the screen will motivate players to keep playing. So not only are we controlled by our own biology, but we are being targeted by corporation’s seeking to take advantage of us and make a profit.

On the plus side, you and I are not like the bee, because we are not eased by our own biology. With self-discipline, we can live the life we truly want.