In some countries of Eastern Europe, including Belarus, Ukraine and Russia, every spring in April people extract birch juice for personal consumption and also to sell commercially. It is a long-lasting tradition carried through generations. Below is an image which shows how juice is collected for commercial purposes for the shelves of local supermarkets. The trees stay alive of course and grow normally, therefore it is not exactly a mass-murder of trees, although it may look this way to an amateur eye.
The juice is commonly extracted by cutting a piece out of the tree trunk and letting the juice fill the container.