Braided rivers are a stunning and rare global phenomenon – waterways that change direction and size, weaving multiple dynamic patterns influenced by rain and glacial shifts.Reged Ahmad speaks to New Zealand correspondent Eva Corlett about how the waterways are now under threat as communities around them have sought to tame and control their flow, leaving Māori tribes to watch the ecological impact with horror. You can support the Guardian at theguardian.com/fullstorysupport