By Simon Gardner COLOMBO, Aug 8 (Reuters) - Climate change threatens to bring further flooding, droughts, fires and landslides and the world must invest now to mitigate damage from natural disasters, the UN's top aid official said on Wednesday. With tens of millions of people displaced in India and Bangladesh after severe flooding, nations should examine ways to protect vulnerable populations, John Holmes, UN Under Secretary General for Humanitarian Affairs said in an interview. "It's the worst we've seen for 50, 60, 70 years and we're beginning to see a pattern of flooding around the world," Holmes told Reuters during a visit to war-torn Sri Lanka. "There is an enormous problem because climate change is a reality already... We need to anticipate it and not just respond to it." "Floods, droughts, fires, landslides, these are already happening in larger numbers than ever before, and I think the link with climate change is well proven." Sri Lanka has escaped the floodwaters choking its South Asian neighbours, but is grappling with its own aid problems. Renewed civil war between the state and Tamil Tiger rebels is hindering delivery of aid to tens of thousands displaced by the conflict and 2004 tsunami. The latest bout of monsoon flooding in India, which began about three weeks ago, is said to be the worst in living memory in parts of the impoverished state of Bihar, where around 10 million people have been affected alone. About 545 people have been killed in the floods, mostly by drowning, disease and snakebites. More than 50,000 people are suffering from diarrhoea in the flood-hit districts of Bangladesh, authorities said. The United Nations is encouraging governments to set up disaster management authorities as well as education campaigns to ensure measures are in place for future disasters. "I think if you invest in disaster risk reduction, and what that means is not building on flood plains, having shelters for people to go to, recognising the problems before they happen and anticipating them, that investment is one of the best investments you can make," he added. Holmes fears that climate change-related natural disasters will pile increasing pressure on a world already short of funding to cope with existing humanitarian disasters. "I think there will be a problem in the future about the scale of the resources," he said. "We never have enough money for the humanitarian crises we have already."