Using the health records of more than a million Swedish conscripts (应征入伍者), a recent study revealed that keeping cardiorespiratory (心肺的) fitness in their late teens and early twenties can cut the risk of developing nine types of cancer by 40% when older. The research team from the University of Gothenburg, Sweden said, "These results could be used to further strengthen the promotion of interventions aimed at increasing fitness in youth."

Almost a third of people aged from 16 to 24 in England aren't physically active, without meeting guidelines of at least 150 minutes of moderate physical activity a week including walking, riding a bike and dancing.

Cardiorespiratory fitness (CRF) measures how well the heart, lungs and linked systems work to get oxygen to muscles during constant activities. The conscripts, aged between 16 and 25, had tests of CRF on exercise bikes between 1968 and 2005. The researchers used Swedish health data to see who went on to have cancer during an average follow-up of 33 years. The study found that increasing fitness was beneficial, regardless of body weight. However, they also found that higher fitness was linked to a higher risk of skin cancer. The researchers explained that this trend might be driven by exposure to sunlight.

Findings from those observational studies provide much evidence for a link between higher levels of physical activity and a lower risk of cancer. However, these studies cannot fully rule out the possibility that active people have lower cancer risk because they engage in other lifestyle behaviors. The researchers cautioned that they had no access to full data on factors such as diet, alcohol intake and smoking and so couldn't fully account for those.

Dr Claire Knight, of Cancer Research UK, said, "The NHS recommends 150 minutes of activity a week, but it's fine to build up activity over time and there are lots of ways to be more active. You don't need to run a marathon or join a gym. Anything that gets you warmer and slightly out of breath and your heart beating faster counts."

Tens of thousands of drone (无人机)owners will have to register their devices for the first time under regulations designed to safeguard privacy.

Rules introduced yesterday require all drones that are fitted with cameras to be logged with the Civil Aviation Authority (CAA). Anyone who fails to do so faces being taken to court and fined up to £1,000. Drones heavier than 250g already have to be registered with the CAA, which costs £9 and must be renewed annually, but the new measures extend this requirement to all devices, including the lightweight models that are used by hobbyist pilots.

The move comes after sharp rise in the number of drones bought by enthusiasts or those operating them for commercial reasons, such as to inspect infrastructure or for photography and filming.

However, the rise has prompted concerns over privacy, with fears that drones are being used to spy on private residences and other buildings. It has also led to an increase in the number of near-misses between drones and other aircraft, including commercial passenger jets. The latest figures show 531 near-misses involving drones were logged in the past decade, including 125 recorded in 2019.

By law drones are supposed to be operated within an operator's line of sight. They have to remain below an altitude of 400ft to avoid interfering with aircraft and flown at least 164ft away from people and buildings. The government has already toughened up regulations in recent years. This includes requiring all operators to pass an online test before being allowed to fly devices. Other changes to the regulations include allowing drones that weigh up to 25kg to be operated, compared with a previous limit of 20kg.

Devices will also fall into three new categories of risk --high, medium and low -- depending on how they will be flown. Low-risk drones, including those typically used by hobbyists, will have operational limitations but will not need authorisation （授权）for flights. Authorisation is needed for larger medium-risk and high-risk drone flights, which are typically carried out in more complex environments, including those beyond the operator's line of sight, which is banned under normal circumstances.

Christian Struwe, the director of public policy, said of the new regulation: "It simplifies different processes and allows customers to travel from country to country without having to worry about different rules in different foreign locations"

In order to get rid of goldenrod from the city, the government of Wuhan is encouraging residents to report any findings of the plant, which is classified as a harmful alien （外来的） species.

Goldenrod is one of the most successful and widespread alien plant species. It is often referred to as "the flower of the devil", as it spreads extremely fast and causes other plants to die.

Besides Hubei province, the plant has also been found expanding in other provinces such as Jiangxi and Zhejiang. Although local authorities have tried to get rid of the plant, it is proving to be a difficult task. Goldenrod represents just one of the alien species that are aggressive towards the country's native species. Statistics show that by 2020, nearly 800 kinds of alien species had invaded （侵略）the country, among which 638 species have invaded the country's agricultural and forestry ecosystems, causing direct economic losses of about 200 billion yuan ($ 31. 36 billion).

At the United Nations Biodiversity Conference held in Kunming, Yunnan province, the invasion of alien species was the subject of discussions, as it was regarded as one of the two most important factors leading to the loss of biodiversity, the other being human-caused ecological damage.

China passed its Biosecurity Law on April 15, 2021, which provides the legal basis for preventing the invasion of alien species and protecting biodiversity in the country. The relevant departments also strictly carry out port inspections and quarantines （检疫）so as to keep harmful organisms out of the country, and they strengthen early warning and monitoring systems so as to address the invasion as early as possible.

However, while government departments are making every effort to prevent and control the situation, the participation of the people should not be ignored. It is also necessary, as Wuhan is doing, to encourage people to pay attention to invasive species and actively play a role in keeping them at bay. Preventing any invasion by an alien species and protecting biodiversity should not just be the government departments fighting alone, but also a people's war.