The Amazon, which holds the world’s biggest river, rainforest and a fifth of its fresh water — is running dry. The region is entering its fifth month of a drought that has been particularly punishing in the northern reaches of the rainforest. …The Rio Negro, a northern Amazon tributary, fell to the lowest levels in its recorded history last month. Wildfires have advanced where waterways have retreated. …The effects of the drought are rippling through the forest. …This year’s disaster follows damaging droughts in 2005, 2010, 2015, 2016 and 2020. Each successive blow — combined with ongoing deforestation and rising temperatures — chips away at the Amazon’s ability to bounce back and puts it closer to a tipping point at which parts of the rainforest could permanently transform into a savanna. …Big droughts used to rarely hit the Amazon — about once every 20 years or so, according to Nobre. But, due to climate change, they’ve come more frequently.