ABSTRACT. - Land Use In Relation To Climate And Hydrology In Finland. Finland is a part of the circumpolar boreal zone. In Europe, the conditions for the humanity in this zone are more advantageous than in Siberia or Canada. So, in the northern Europe the impact of man on nature has been and still at present is more powerful than in the other parts of the zone - and in Finland more powerful than in northern Russia or Scandinavia because Finland has not any regions with a better climate to exploit like its neighbours. Two huge pure national measures done by Finns can be recognised. The ancient burn-beating culture means that rye was grown in ash on small plots in forests, being in advance logged and burnt; because only one or two yields were taken at a time so that the cultivated plots continuously rotated in the forests, the method required huge areas so that people could be nourished, without any permanently cultivated fields, only if the population density was less than 3 inh. per sq. km. Circa 150 to 200 years ago this limitation was neglected by people in the south-eastern Finland so that forests were replaced by bushland, which resulted in a crisis of the society and huge floods. Since 1950 till 1990’s, huge mire areas were drained in order to make them to produce timber, and lately, to dig peat. This national project has various effects on climate and waters, part of them being temporary, part permanent.