When lost, it is possible to use trees to assist you in navigation. In northern temperate climates, moss will grow on the northern side of the tree trunk, where it is shadier. Failing that, if you find a tree that has been cut down, you can observe the rings of the tree to discover which direction north is. In the northern hemisphere, the rings of growth in a tree trunk are slightly thicker on the southern side, which receives more light. The converse is true in the southern hemisphere.