*Review* **UAVs for Vegetation Monitoring: Overview and Recent Scientific Contributions**

**Ana I. de Castro 1,\*, Yeyin Shi <sup>2</sup> , Joe Mari Maja <sup>3</sup> and Jose M. Peña <sup>4</sup>**


**Abstract:** This paper reviewed a set of twenty-one original and innovative papers included in a special issue on UAVs for vegetation monitoring, which proposed new methods and techniques applied to diverse agricultural and forestry scenarios. Three general categories were considered: (1) sensors and vegetation indices used, (2) technological goals pursued, and (3) agroforestry applications. Some investigations focused on issues related to UAV flight operations, spatial resolution requirements, and computation and data analytics, while others studied the ability of UAVs for characterizing relevant vegetation features (mainly canopy cover and crop height) or for detecting different plant/crop stressors, such as nutrient content/deficiencies, water needs, weeds, and diseases. The general goal was proposing UAV-based technological solutions for a better use of agricultural and forestry resources and more efficient production with relevant economic and environmental benefits.

**Keywords:** drone; RGB; multispectral; hyperspectral; thermal; machine learning; water stress; nutrient deficiency; weed detection; disease diagnosis; plant trails
