Environmentally friendly sculptures and modern sculptures differ in their design, materials used, and purpose. Environmentally friendly sculptures are meant to be understood by viewers and use natural materials like wood to share a message about environmental protection, while modern sculptures have complex designs made from materials like plastic that can harm the environment and are intended more for aesthetic purposes than conveying a message. Both types of sculptures reflect modern times rather than historical styles, with environmental sculptures taking inspiration from nature and modern sculptures exhibiting styles like cubism.