This study addressed this shortfall by taking two important steps subsequent to the modelling
of livestock densities. In the first step we develop a new approach whereby the proportion
of extensively raised chicken or pigs is modelled as a function of gross domestic product (GDP)
per capita (in purchasing power parity for 2010 (PPP2010)), based on the following assumptions.
The consumption demand for animal products per capita, expressed in kg of meat consumed
per person per year, was previously shown to be strongly linked to GDP per capita [35].
So, increasing incomes creates higher demand for animal products and this represents a strong
economic incentive for investments in intensification. A corollary is that the investment
needed by a producer to intensify its production units may also be more easily found in an
economy with rising income. Agricultural development also largely contributes to rising GDP,
especially in poor and transition economies, which further supports the links between intensive
production and GDP. Given the size of China compared to other countries, and the strong differences
in economic development and policies for different provinces, the GDP model was
developed and applied at the country-level in all countries except in China where provincelevel
data were used. We then used this model to predict the proportion of extensively raised
animals in countries where the figure was not found through data-mining and to distribute the
estimated number of extensively raised animals as a function of the human rural population,
estimating commercially raised chickens by difference from the total, and adjusting for the rare
pixels where the predicted number of extensively raised chickens exceeded the total number of
predicted chickens.