The study looked at how well plants in South East Europe turn carbon dioxide into plant material under stressful conditions like drought. Using data from NASA's MODIS instrument, researchers found that drought can reduce this efficiency by 10 to 20%, causing the region to release more carbon into the atmosphere instead of storing it. Forests are hit the hardest by drought, especially when it lasts for five months. The impact on plant productivity and carbon efficiency is most severe during these long droughts. The severity of the efficiency drop depends on how strong and long the drought is, as well as when it happens during the year. More research is needed to understand how high temperatures and lack of water affect plant carbon use efficiency.