A fourth and penultimate round of talks on a United Nations treaty to combat plastic pollution will begin in the Canadian capital Ottawa on Tuesday. Representatives from more than 170 countries are expected to attend the negotiations, which are scheduled to run until next Monday. “This negotiation is pivotal,” said UN Environment Programme official Jyoti Mathur-Filipp. “It is an opportunity to make significant progress for a robust agreement that would allow future generations to live in a world free of plastic pollution.” Pressure is rising on delegates to reach a draft agreement ahead of the…