Usually, none. Looking at statistics from the United States, for which the most complete records exist, only about 2% of tornadoes result in human fatalities. Among killer tornadoes, most only kill one person.
usually hundreds if it is a minor tornado but if it is major, usually thousands of people.
No. A tornado is a localized event, usually not affecting more than a town or two. A tornado may lead to people leaving a town, or sometimes a tornado-prone region, but not usually a country. For example, many people left the small town of Greensburg, Kansas after most of it was destroyed by a tornado in 2007, but they all stayed in the United States.
Tornadoes are usually accompanied by rain and often by hail. However, many tornadoes form in a precipitation-free part of the parent thunderstorm.
On average, tornadoes in Canada are responsible for causing 10 fatalities per year. However, this number can vary widely from year to year depending on the severity and frequency of tornado events.
The most significant effect on a natural habitat would be the destruction of trees. Even a tornado that is not particularly intense can snap and uproot many trees. The area affected is usually not very large, but it can take decades to fully recover.
The Greensburg, Kansas tornado of 2007 Killed 12 people and injured 63.
The Andover tornado killed 17 people.
The Tri-State tornado killed 695 people.
The Waco, Texas tornado killed 114 people.
The Daultapur-Saturia tornado of 1989 killed an estimated 1,300 people.
There were no tornado fatalities in Florida in 2010.
The Waco, Texas tornado of May 11, 1953 killed 114 people, tying it with the 1902 Goliad tornado as the deadliest tornado in texas history.