Why are the leaves of Ephedra small and scalelike?

The leaves of Ephedra are small and scalelike primarily as an adaptation to their environment. Because these gymnosperm shrubs typically inhabit dry, desert regions, the reduction in leaf surface area is necessary to minimize water loss through transpiration.1

In these plants, the bulk of photosynthesis is carried out by the green stems rather than the leaves, allowing the plant to survive in arid conditions where water conservation is critical.1