Once again, commercial vessels sailing in the Red Sea are being attacked. Our correspondent explains why Houthi rebels, an Iranian-backed militia in Yemen, have regrouped. The islands of Tuvalu are sinking. Now Australia is offering residents the world’s first “climate visas”. And remembering Dutch agronomist Simon Groot.Listen to what matters most, from global politics and business to science and technology—Subscribe to Economist Podcasts+For more information about how to access Economist Podcasts+, please visit our FAQs page or watch our video explaining how to link your account.