What are some environmental impacts on migration? why do people live/settle in areas affected by hurricanes, earthquakes, wild fires, rag. if they leave, will they comeback? why or why not is any of tract of land truly free from human influence? why or why not

I guess an environmental impact of migration MIGHT be that the receiving country obviously will rise in population so it'll have to expand and also use more resources to sustain the extra people. Therefore, more land is urbanized which isn't great for habitats and animals, more land will have to be farmed - loss of animal habitat - and more energy will have to be used to power homes etc. 

People may live in an area thats at high risk of hurricanes (etc) for the reason  that they have no choice. Or maybe, in a place like Japan where they have the best warning systems and highly developed buildings, it doesnt really matter as much to them. On the other hand, people will live near volcanoes because the soil is much more fertile due to the volcanic ash. This means they can grow more food from the same soil - maybe its a risk worth taking? 

If a disaster happens, some may not come back simply because its too dangerous - on the other hand, some might only move temporarily to recover or while their home is rebuilt. Tourists may not come back because it is too dangerous but it will also attract tourists because not everyone can witness a volcano or be in an earthquake. 

Lots of land is free from human influence (at the moment) simply because its probably too difficult for us to settle. For example, a desert like the Sahara in Africa is EXTREMELY dry and dangerous. People have been there but it isnt constantly under human influence. Assuming our technology improves and we keep growing in population, maybe everywhere will one day be influenced by humans in some way. 

Hope this helps :)  

Wildfires maybe because it depends the agriculture

The answer is the magnetosphere.