This video provides an overview of direct and indirect effects of increases in atmospheric CO2 on coastal wetlands using a salt marsh-mangrove community as an example. A short background is given summarizing past, present, and future predicted changes in CO2 concentrations based on ice core data and direct measurements conducted at monitoring stations such as the Mauna Loa Observatory. Responses of plants utilizing different photosynthetic pathways (C3 vs. C4 species) are used as a starting point to explain potential responses of a coastal plant community containing Avicennia germinans (C3 mangrove) and Spartina alterniflora (C4 grass) to changes in CO2 and associated climate change (temperature, rainfall). Experimental methods used to study effects of CO2 on plants are described, and results of peer-reviewed studies are summarized to illustrate the complexity of potential effects of CO2 and climate change on coastal wetlands. Conceptual models are also used to illustrate direct effects of environmental change and interactions among various climate drivers and the plant community.