great sb!! you have a great sense of color with skin, you paint it wonderfully!! keep doing those enviro studies and figure drawings, and of course try to understand the form from an anatomical point of view.
you could improve the depth in your environments, what is further away from the camera fades away, no only in value but also in definition, objects farther away will be less defined and so they will have less detail and objects closer to camera will be more defined and detailed. Try using more defined and crisp edges to what is closer to camera , in the study of the desert, the cactus closer shood have the edges clearly defined and more crisp in comparison to one further away. try controlling your lines and edges it will add depth to your environment studies just my two cents lovely work i will keep on eye on your sketchbook ^^