*The new site art still not complying with the copyright requests of the artist... see comments
The artist seems like a really great guy who likes nature and hiking and likely subsidizes his income with his cartoons so that he can do more treks in nature. Lucky for you he is a really nice guy, because most of his hiking cartoons and wildlife sketches are free... as long as you use it in the original form and don't try to profit from it... It is really popular, which you all could have found by doing an image search that took me 3 seconds max.
For the very few he does charge for, his price is between 100 to 200$ for use.