The Concept of Agricultural Productivity on Ecosystem Scale and Its Measurement

What is the connotation and the extension of the productivity concept and how to calculate it are the core problems in evaluating an agricultural-production process. The attributes of agricultural production processes have changed greatly in the last 100 years, and the methods to describe and measure the productivity failed to keep in pace with the production processes, resulting in a totally vague, incomplete evaluation of the production processes. Sometimes the serious problem of pollution is ignored in the race to shortdated money making, thus leading to a blooming and flooding pollution; sometimes the great ecological benefits are ignored and the corresponding production processes suffer drastically from “economic deficit”. With the old agricultural productivity indices, no prediction can be made of the ultimate effects of agroecosytem on mankind-pollution or welfare. A new concept, agricultural productivity on ecosystem scale (APES) and the related indices are defined here to solve these problems. Emergy and exergy are introduced to help the measurement of the indices. Emergy is the memory of energy, which can be used to measure the total cost, including natural capital and social capital. APES of the agroecosystem is the aggregated contributions of all components to mankind and its habitat in uniformed dimensions, it may be expressed in material, energy, information, organization, pollution and damage, etc., positive or negative, and are calculated based on exergy methods. And a related index agroecological coupling degree (ACD) shows sustainability.