Kees van Leeuwen conducts research on the concept of terroir in viticulture. His works are centred on environmental constraint in the expresssion of vine-growing terroir. This constraint is most often a limiting of water supply or a limiting of nitrogen nutrition in the vines. Kees van Leeuwen has taken part in the creation and evaluation of several indicators of vine water and nitrogen status in vines. Kees van Leeuwen has also worked on the climate’s effect on the expression of vine-growing terroir. The vine’s response is evaluated through the precocity of its vegetation, its growth and development, and its grapes’ constituents at ripeness. Particular attention is paid to the grapes’ aromatic potential in relation to environmental factors. He participated in the creation of the Grapevine Flowering Veraison model (GFV model). His research focusses particularly on the effects of climate change in viticulture and how growers can adapt to a changing environment.