Complex sentence: The fur trade kept the interest in Frances overseas colonies alive, yet only encouraged a small population as minimal labour was required, and also discouraged the development of agriculture, the surest foundation of a colony in the New World.
Split into simpler sentences: The fur trade kept the interest in France's overseas colonies alive, yet only encouraged a small colonial population, as minimal labour was required. The trade also discouraged the development of agriculture, the surest foundation of a colony in the New World.