Ground level ozone is toxic to plants, entering leaves and damaging them to reduce productivity. Ozone pollution concentrations will likely rise worldwide as wildfire becomes more common, since smoke can interact with downwind local conditions to produce ozone. However, wildfire smoke may actually help plants by improving how efficiently they use sunlight and by blocking some ozone from entering leaves. We used a network of sites across America that measure ecosystem productivity in many different climates to study how environmental factors like temperature, rainfall, air moisture, ozone, and smoke affected growing seasons and total yearly productivity. We found that ozone pollution strongly shortened the growing season while smoke offset some of the effects of ozone pollution by lengthening the growing season. Total yearly ecosystem productivity was greatly reduced by ozone pollution - twice as much as by drought stress. These findings demonstrate that ozone pollution significantly affects ecosystems and should be included in future climate change assessments of ecosystem productivity.