Also, how to decide which conservation action to apply in prioritize areas, and How environmental authorities can get involved in what type of conservation actipn?
It's always tricky to define which area is important or must be prioritised.
Instinctively a top priority protected area must be rich in biodiversity, host a particular threatened or endemic species, or even include a unique landmark. These can, of course, be combined. At this point, and once the limits are defined, you'd have an area of international importance. I'd say, what makes it a priority to protect it, is the presence of imminent threats (poaching, land use etc). Once you know what those threats are, taking immediate action to mitigate the pressure becomes your priority in terms of conservation. Later, actions such as restoration, reintroductions etc may happen. However, remember that the protected environment must be sained before taking any further actions. For instance, there is no need to reintroduce rhinos in a place where poaching is common.
Another way of defining important areas can be found in the ramsar convention on wetland which defines 9 criteria, which can be applied/adapted to pretty much any situation. https://www.ramsar.org/sites/default/files/documents/library/ramsarsites_criteria_eng.pdf
It depends on your objective. Conservation projects may focus on the wildlife, biodiversity, ecology and management of both fauna and flora. Or you may focus on the social aspects of conservation that deals with the benefits that conservation can bring to the indigenous people such as health, education, income opportunities and community empowerment.
There can be several variables such as socio-economic, biodiversity (RET species, level of exploitation of flora and fauna), infrastructure related (new development project in the nearby area), a specific tribal community, occurrence of disasters etc such as forest fires, land slides in the watershed/catchment etc. that may affect the area to be considered as conservation area. These variables are site specific and are selected based on local knowledge. For a national and regional level analysis they can be selected using exploratory analysis.
Today micro waves and other natural resources disestar and anthropogenetics activities are reaching out to the species for that straight and strict conservation guideline required than only it can.
40 years ago Chris Margules and I reviewed the various criteria which had been used - there are many (see Margules & usher (1981). Criteria used in assessing wildlife conservation potential: a review. Biological Conservation, 21, 79-109). From the point of view of what grows/lives in an area of land or sea, perhaps species richness, rarity and endemicity are the most frequently used and probably the most important. Characteristics of the land or water can also be important - the larger the better, and linking with other protected areas is useful, but this depends on the resources available to you or an organisation.
Conservation priorities that are based on species distribution, RET species. Species with their functional roles and evolutionary histories are also included. To ensure that priorities are biologically comprehensive, various factors of diversity may be considered.