Finnish Lakes

Description

From the estimated number of 10–15 million lakes in the world, well-over half are located in the northern boreal zone. In Finland, a detailed lake inventory was made in the 1980s with the following results (Kuusisto and Raatikainen, 1988):

Area (km2)	Number of lakes
>100	47
10–100	279
1–10	2,283
0.1–1.0	13,094
0.01–0.1	40,309
0.0005–0.01	131,876

This brought the total number to 187,888, over three times higher than the previous estimate published in the 1950s. The increase was simply due to the myriad of ponds smaller than 1 ha, their number being as high as 131,876. The lower size limit was set to 0.05 ha.

In practice, these figures can naturally not be accurate to the last digit. The sizes of water bodies vary according to hydrological conditions, causing them to cross class boundaries. The shores of shallow lakes are not well defined on the basic maps 1:20,000, which were used in the work. All map sheets, 3,610 of them, were checked twice; the work too over two...