Survival skills
A human being can survive an average of three to five days without the intake of water. The issues presented by the need for water dictate that unnecessary water loss by perspiration be avoided in survival situations. The need for water increases with exercise.
Space and survival
Many of the same existential risks to humanity would destroy parts or all of Earth's biosphere as well. And although many have speculated about life and intelligence existing in other parts of space, Earth is the only place in the universe known to harbor life. Eventually the Earth will be uninhabitable, at the latest when the Sun becomes a red giant in about 5 billion years. Mankind, or its intelligent descendants, then has to leave the Solar System to ensure survival of the human species.