6.19 Natural growth of non-cultivated biological resources (K.5) is not under the direct control, responsibility and management of an institutional unit and thus is not production. The increment in these economic assets such as standing natural timber, or fish in the estuaries, must then be regarded as an economic appearance.
6.20 Natural growth should be recorded as an addition (K.5); the depletion of these resources should be recorded as an economic disappearance (K.61). In practice, however, natural growth can only be recorded net because the physical measurements that are likely to be the only basis available for the recording are, in effect, net measurements.