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More than 60% of the animals used for science across the European Union in 2017 were mice.Credit: Whitney Hayward/Portland Press Herald/Getty

The use of animals in scientific research seems to be declining in the European Union. The drop follows the introduction seven years ago of legislation designed to reduce the use of animals in research and minimize their suffering. The first report on the state of animal research in the EU since the change says that 9.39 million animals were used for scientific purposes in 2017, compared with 9.59 million in 2015.

Nature | 3 min read

Preprint repositories such as IndiaRxiv, ArabiXiv, AfricArxiv and INA-Rxiv (from Indonesia) boost the visibility of regional science, but finding cash to run them is proving difficult. Some discipline-specific repositories, such as EarthArXiv and MarXiv (for marine-conservation science), are also struggling. At issue are new fees introduced by the non-profit Center for Open Science, based in the United States, which hosts 26 such repositories.

Nature | 5 min read

In this three-minute guide to how scientists are fighting COVID-19, discover the fields of research that are crucial to keeping outbreaks under control: epidemiology, virology and biomedical science. (Nature | 3 min video)

Features & opinion

A tropical forest in the Bribri Indigenous region of Costa Rica.Credit: Ivan Kashinsky/Panos

There is a quick, cheap way to lower carbon emissions and protect the more than three-quarters of species that live in the tropics: reduce tropical deforestation. To pay for it, an economist, a conservationist and the environment ministers of Colombia and Costa Rica argue for a levy on fossil fuels. Their analysis shows that, if 12 other countries with tropical forests roll out a carbon tax similar to Colombia’s, they could raise US$1.8 billion each year between them to invest in natural habitats that benefit the climate.

Nature | 10 min read

The upside of irreproducibility can be found in attempt to measure the precise value of the constant of gravitation (G) — which is still uncertain despite numerous experiments spanning three centuries. When results in the science of measurement cannot be reproduced, argue metrologists Martin Milton and Antonio Possolo, it’s a sign of the scientific method at work — and an opportunity to promote public awareness of the research process.

Questions in biomedicine and the social sciences do not reduce cleanly to the determination of a fundamental constant of nature. But metrology reminds us that irreproducibility should not automatically be seen as a sign of failure, argues a Nature editorial. It can also be an indication that it’s time to rethink our assumptions.

Nature Physics | 9 min read & Nature | 4 min read