Quantifying leucaena cultivation extent on grazing land

Leucaena is a perennial fodder crop that can significantly improve beef production across substantial parts of the world’s grazing lands. We surveyed leucaena cultivations across 350 000 km2 of Australia’s prime leucaena-growing region, using a new approach to quantify leucaena coverage and distribution. This approach uses high resolution imagery to detect leucaena by the distinctive alley cultivation pattern that is typical in the region and in many other parts of the world. We estimated there are ~123 500 ha of leucaena in the study region. Although no prior estimate of leucaena coverage has been based on exactly the same geographic area, our data strongly suggest that recent published estimates of leucaena coverage for Queensland and Australia are substantial overestimates. In addition to providing robust estimates of total leucaena coverage, we demonstrate how the method can also contribute to other survey objectives such as comparison of actual with potential spatial distribution, and assessment of statistical sampling power. We also discuss the potential application of the new method in international contexts.