Some of the largest and longest living plants that exist, trees have been represented throughout art history with extraordinary variety. As a subject, trees allow artists to explore interesting light and shadow effects through their branched canopies, vibrant colors as leaves change with the seasons, and a host of life forms including nesting birds and swinging monkeys. Considered a symbol of wisdom, the tree of the knowledge of good and evil is a popular Christian theme, notably repeated throughout the career of Renaissance painter Lucas Cranach. Romantic landscape painter Caspar David Friedrich casted trees as spiritual markers of the sublime, setting them amidst ruined Gothic churches or cemeteries. Modernist Emily Carr painted forest scenes inspired by the land of the indigenous people of the Pacific Northwest Coast in order to draw attention to the environmental impact of industry. Arboreal themes continue to fascinate contemporary artists, such as Land artists Christo and Jeanne-Claude who have wrapped trees in translucent polyester bubbles, sculptor Roxy Paine who builds lifelike spindling trees out of metal, and painter Benjamin Butler who uses the tree shape as a vehicle to explore abstraction.