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On March 31, 2019, a wildfire in Liangshan Yi autonomous prefecture（凉山彝族自治州）led to 31 deaths, including 27 firefighters. And on May 1st, 2016, in Alberta, Canada, a wildfire destroyed an area of nearly 700 square miles. More than 88, 000 people had to leave their homes and thousands of homes were destroyed.

Wildfires are unexpected, unplanned. And the cause of most wildfires is unsure. To burn, wildfires require the right conditions-fuel, oxygen and heat. And global warring is one of the most important reasons. The high temperatures and dry conditions make the fire spread quickly.

In many parts of the world, wildfires happen naturally. They are started by lighting（闪电）or some other special weather conditions. In recent years, there have been more wildfires because of dry, hot weather, and changeable weather patterns because of global warning.

However, many fires are started by people. Sometimes, people clear land for farming. Besides, there are smokers who accidentally set fires.

Wildfires can cause a lot of smoke, which will pollute the air. Lots of lives, property（财产）and valuable forests will soon disappear in wildfires. When trees are burnt down, and heavy rain follows, more disasters such as terrible floods will happen.