Maybe because of Tragedy of Commons?

https://en.wikipedia.org/wiki/Tragedy_of_the_commons

People, data, technology, commitment of the organization. Probably one of these four things is not quite sufficient.

Three fundamental factors to determine the success of participatory natural resources management are: tenure security, decision making power and the capacity of the community being involved in the practice. Inadequacy in one or more of these factors and imbedded sub-factors may lead to the failure of the CBNRM policies or programs. 

Because resource use/ownership rights (partly tenure as referred by Narayan) and/or community (e.g. membership rules) are fuzzy. Please see under Conservancies in the attached.

Article The living commons of West Tyrol, Austria: Lessons for land ...

Chapter Of pastures and tourism. A comparison of Tyrolean and Namibi...

Most of us assume a lot in Community Based Resource Management. The reason is we tend to shift the answers towards our liking but in actual fact, Communities were living with the resources long before our ideas. All we need to do is take a closer look at the history of resource use in the study area over a period before we can move our ideas into it. Written history is not available but we have to look at verbal recounts of events in the use of resources. This can inform us in our thinking and develop strategies based on the history.

It has a lot to do with the expected benefits. i) The 'benefits' that are often 'agreed' to by the communities are just 'tokens' and reflect what the 'managers' can allow. In many cases, these are different from what the communities are interested in, but may not disclose openly because they know what the 'managers, would want hear. ii) Many of the benefits can not even improve their livelihoods. Many, so called, 'community' members are  happy receiving the benefits individually  - rather than the collectively. I attach an article (Bitariho et. al. 2015) on the experiences around Bwindi Impenetrable Forest in western Uganda

You may try to look at the work of Elinor Ostrom and her Design principles for Common Pool Resource (CPR) institutions

Ostrom identified eight "design principles" of stable local common pool resource management:

1.    Clearly defined boundaries (clear definition of the contents of the common pool resource and effective exclusion of external un-entitled parties);

2.    Rules regarding the appropriation and provision of common resources that are adapted to local conditions;

3.    Collective-choice arrangements that allow most resource appropriators to participate in the decision-making process;

4.    Effective monitoring by monitors who are part of or accountable to the appropriators;

5.    A scale of graduated sanctions for resource appropriators who violate community rules;

6.    Mechanisms of conflict resolution that are cheap and of easy access;

7.    Self-determination of the community recognized by higher-level authorities; and

8.    In the case of larger common-pool resources, organization in the form of multiple layers of nested enterprises, with small local CPRs at the base level.

community based natural resource polices not successful, not integrating  the indigenous knowledge systems in natural resource management

Hi Irene

You seem to refer to top down approaches. Could you provide the referred policy document for my interest and use?

To Yuri, the tragedy-of-commons has been de-constructed many times over. By Ostrom on a grand scale (see Michael above); my attached papers specify the detail on pasture and game. Please read the original Hardin paper and see for yourself that this is not science by any standard. His original article is Malthusian without  a single empirical fact, not even a location. He may refer to the historical commons in UK, or to the contemporary western federal rangeland in the USA. 

The tragedy-of-commons has also been paraphrased as tragedy-of-exclusion (of landless residents, as applies to my current municipality of residence) at the time period of enclosure/partition of the commons) and tragedy-of-privatization by another author. In order words, a tragedy-for-whom would seem a valid question.  

In part, maybe because it is not inserted in an effective and well established official  functional governance structure, where involved parts (stakeholders) are not strongly and conciously compromised nor have received the enough relevant capacity bulding to act accordingly.. For example, Integrated Coastal Management should be effective when well established and effectively supported and implemented as an adequate governance process) supported by relevant stakeholders, includding governrment at the relevant levels (municipal, province, and National levels).. This should be supported an adequate and well  accepted legislation platform. 

yes, Pedro, the direct and indirect users of the mangrove (ecosystem) should get organised as a legal person (foundation, company what ever applies in context) to prepare for negotiations with developers of shrimp ponds etc. and ultimately access to the courts. 

Embarking on an exclusive CBNRM may be problematic; in contemporary times, scholars and practitioners argue for a collaboration between community actors, state actors and NGOs to prudently create value for people and environment. Embarking on this requires some key social and technical processes. kindly follow the article below

Yeboah-Assiamah, E., Muller, K., & Domfeh, K. A. (2016). Rising to the challenge: A framework for optimising value in collaborative natural resource governance. Forest Policy and Economics, 67, 20-29.

http://www.sciencedirect.com/science/article/pii/S1389934116300089