Standardizing the calculation of the annual rate of deforestation

Different authors utilize different formulae to calculate the annual rate of change of forest cover (or its opposite, the annual rate of deforestation) and use different terms to describe it. This generates confusion. I suggest that the annual rate of change of forest cover should be calculated as: r = (1/(t(2) - t(1))) x ln(A(2)/A(1)). This formula is derived from the Compound Interest Law. It is also derived from the mean annual rate of change and for this reason, is more intuitive than the formula used by FAO [q = ((A(2)/A(1))(1/(t2-t1))) - 1]. The rate r is always higher than q, but in most cases, the difference between the two quantities is lower than the sampling error. The rate r is significantly higher than q only when deforestation is extremely high. To ease comparisons between sites of annual rates of forest change, the forest area, time of measurements and formulae used should be clearly indicated. (C) 2002 Elsevier Science B.V All rights reserved.