Pakistan Prime Minister Imran Khan said that the world will have to pay a heavy price if the environment is not well protected and the issue of climate change and global warming is not addressed properly. Speaking at the Pakistan-hosted World Environment Day event in collaboration with the UN Environment Program here on Saturday, Khan said that nature has given his country and the world another chance to mend its ways and take steps to protect the environment to overcome the losses humans incurred to the planet, Xinhua news agency reported.Regarding the issue of global warming, Khan expressed serious concerns over the glacier melting phenomenon in South Asia including in the north of his country, stressing to take urgent steps to stop the melting."Global warming is affecting the whole world but the countries whose water supply is dependent on glaciers including Pakistan will be worst hit. Over 80 per cent of our water needs are met by glaciers which are melting fast, and if the situation remained the same, a serious water shortage is feared to occur in the future."Talking about the measures taken by his country to protect the environment, Khan said that the government has launched the '10 Billion Tree Tsunami' program and 1 billion trees have already been planted while 9 billion more are expected to be planted over the course of next three years.He also paid tribute to forest guards who faced challenges from the timber mafia and some of them lost their lives in the line of duty. Khan urged the developed countries to help developing nations in their fight against climate change, because initiatives like planting 1 billion trees put an economic burden which is determined to protect the environment, not for its own sake, but the world too.