Most of us have experienced the simple pleasure of shade on a hot summer day. Hot days are more than just uncomfortable, they are an important health concern. And, with climate change in full swing, heatwaves and extreme heat are becoming more common. Urban trees offer a natural cooling system, mitigating some of this heat — and according to a new study, they save lives and prevent plenty of visits to the ER. But the same study also reveals a stark disparity: neighborhoods with fewer trees, often home to people of color and low-income residents, suffer more from heat-related health issues. We …