Watchers can use whatever they consider relevant to do their mission. IBISA encourages them to use different tools and provide feedback on these tools.
Having said that, IBISA has developed a platform that primarily use two main sources:
1- European Commission JRC that operates a global observatory of drought, flood, earthquakes and miscellaneous natural catastrophes. The information is less fine-grained than the other sites, but it produces detailed reports and complements well the others. For example here.
2- IBISA’s custom script in order to calculate the NDVI anomaly and show it visually. The NDVI anomaly is calculated by taking the average NDVI value for the current month and compare it to the average NDVI value of the same month of the last 3 years. In that sense, a negative anomaly is what we call a damage severity. This script was awarded in May 2019 the first prize in category Agriculture and Forestry in a Sentinel Hub EO script contest at the Living Planet Symposium of the European Space Agency. This script can be visualised using Sentinel Hub playground