The value of defining Essential Variables
A need that takes the form of a timely demand is the systematic monitoring of weather and climate. Such a need arises from the fact that scientific knowledge and understanding has reached really big heights and its furtherance would demand very detailed and high-resolution observational information that would enable the infilling of current gaps in the scientific knowledge . Apart from that, though, high resolution observational datasets are also needed for informing the decision making process for a wide variety of applications. The aforementioned, accompanied by the fact that there was a recent decrease in the effort put to maintain and enhance the contribution of observational networks in many areas world-wide, made it necessary that a coordinated and orderly way of performing such a procedure should be established.
For this reason, the Global Climate Observing System (GCOS)  developed the idea of constructing a set of “Essential Climate Variables” (ECVs) , that would aid the understanding and monitoring of the evolution of climate, would additionally facilitate the planning of mitigation and adaptation measures and finally, would abet in climate service applications. According to Bojinski et al., (2014) an ECV is defined as a: “physical, chemical, or biological variable or a group of linked variables that critically contributes to the characterisation of Earth’s climate”. A list of the ECVs delineated thus far is presented in Table 1. A really noteworthy point concerning the collection, assessment and use of ECVs is the massive contribution of the Earth Observation (EO) systems, which are estimated to cover for the majority of ECVs .
Following the same approach for the successful monitoring and assessment of changes in Essential Climatic Variables, the Group on Earth Observations’ Biodiversity Observation Network (GEO BON)  initiated the collection of Essential Biodiversity Variables (EBVs) , that would inform policies related to conservation, planning and activities related to ecosystem services. Equivalently to the ECVs, the EBVs aim at monitoring the state of biodiversity at various levels and scales .
As it is seen thus far, there is an increasing need in various disciplines for a coordinated strategy on the definition of variables that need to be systematically monitored, so that changes in these variables can be effectively assessed. On the contrary to ECVs, there is a deficiency in monitoring EBVs from space, due to the limited amount of Earth Observation products that could potentially be translated to EBVs. A recent Nature paper  proposed that this issue in biodiversity mapping could be potentially addressed by spatially interpolating point samples to gridded continuous maps, regarding species distribution.
 GEO BON