Protected Areas (PAs) are fundamental for conserving biodiversity. If well managed, PAs preserve endangered species, healthy ecosystems and ecological processes, generating benefits including several environmental services [1–5]. However, global conservation efforts face increased human pressures on natural ecosystems continues to decline [6].

A good management plan (MP) is essential for an effective PA and must contain clear strategies to achieve goals for nature conservation and human well-being. Furthermore, MPs should address the context of the region [3,7]. This assessment, or diagnosis, should identify the ecological condition of the PA, values for conservation, social aspects and the threats to the area. It indicates “where we are”, and it is key to “where we want to reach”, and the “how we get there” [8]. Relevant ecological data are needed to support good management [9], but the research produced does not always satisfy the needs of the conservation and decision-makers [10]. However, research on different areas should answer questions for effective management of PAs. These surveys make up the initial phase of planning. Diagnoses can use data from different sources, such as long-term biological inventories, Rapid Ecological Assessments [11], local communities’ knowledge, or workshops with specialists [9,12], produced specifically for the MP (primary data) or from researches or technical reports made for other objectives, does not related to MP (secondary data). However, the information gathered is not always integrated, resulting in only extensive descriptions, which are not very useful for planning the management of a PA. The identification of conservation targets and their threats and the spatial distribution of these elements would be more effective for defining the objectives and results for the conservation of a PA and the management strategies to reach them [12–14]. They should also support the monitoring of conservation effectiveness [8].

The strengthening PA management in Brazil—designated Conservation Units—is particularly important, covering 18.6% of its continental territory and 26.5% of its marine territory [15]. These areas are responsible for conserving megadiversity and ecosystem services of global magnitude [2]. However, the threats to these PAs are increasing, ranging from over-exploitation of biodiversity (hunting, fishing and the collection of timber and non-timber products), habitat loss through the advancement of agribusiness, to large mining and hydroelectric projects [16], and fire, which is increasingly frequent in PAs in fire-sensitive Amazonian forests [17], or in fire-prone ecosystems, like the Brazilian Cerrado [18].

About half of the 334 PAs managed by the Brazilian federal government have MPs. A main barrier to the MPs has been elaboration of diagnoses of the physical, biological and socioeconomic aspects, since they require a long time, financial resources and have been of little use for effective PA planning. However, despite criticism of this important planning stage, there are no deeper assessments of its design and there are no concrete proposals to change it. In this work, we present an overview of the environmental diagnosis carried out in support of MPs by evaluating the methods used and the analyses carried out to support management decisions. We also make recommendations for improving the process of developing MPs, to contribute to more effective nature conservation.

The use of secondary data in most diagnoses shows there is some scientific knowledge about Brazilian PAs. Especially in Extractive Reserves, the basic information for planning was also derived from participatory workshops. Local knowledge is an important source of information about PAs, but it must be combined with scientific evidence in planning [9,28]. Information such as the amount extracted from the resource and maximum sustainable yield are needed for sustainable management and to reach objectives of biodiversity conservation [29]. However, most Extractive Reserves lack specific management studies and the few existing cover few exploited resources. Although these communities use natural resources over many years, keeping the area apparently preserved, we can not assume that its use poses no risk. Instead, the use of resources, especially when linked to a commercial chain, can become a complex long-term problem depending on the scale, type of use, and the fragility of the environments and species used [30]. All uses of biodiversity, legal or illegal, if not monitored, may affect the ability of a PA to achieve its conservation objectives [7]. Furthermore, the greater the risk or more serious consequences of management actions, the greater the need for scientific data and analyses to support decision-making [31]. It is necessary to equalize the objectives of Extractive Reserves to ensure the achievement of the Goals of Aichi but also seeking results for conservation of nature beyond social results [29,30].

The rarity of MPs using secondary data from research programs to support management, monitoring and conservation of these areas demonstrates a weakness in the Brazilian PA system [9]. Since extensive research is a barrier to prepare MPs due to the time required for data collection and analysis, the generation of scientific knowledge should be a constant and priority action of management programs. The absence of these programs makes it difficult to monitor conservation effectiveness and is a gap for adaptive management. In addition, access to scientific information for decision-making and knowledge transfer among research institutions, conservation planners and managers should be improved [32].

The use of the data is even more important than the methods. Despite the environmental characterization presented for all PAs, the level of diagnosis is low, independent of PA category. The description of PAs is prioritized to the detriment of data analysis and generate little information for decision-making. The amount of data presented in MPs does not necessarily mean there is quality management information, since the information may not be relevant to the management challenges of the PA. The insufficiency of analysis in environmental diagnoses shows that, even when descriptions of the ecological elements of PAs are made, they are not very effective in the analysis of this information and its transformation into useful information for planning. In many cases, the data obtained are general and purely descriptive, not providing the necessary information for decision making by managers. It would be relevant information, for example, analysis of threats on species or environments and their consequences and possible strategies to minimize them. Data obtained in a targeted and well-analyzes manner are essential to support decision-making for the management of natural areas.

Identification of threats provides key information, but although it was widely used among MPs, it has been presented in most of the plans in a scattered manner, non-systematized, without clear connection between threats and their impacts on conservation. Moreover, in general threats were not related to their real causes, leading planners to focus on the problem rather than on its origin. Unfortunately, the roots of threats also tend to be ignored when they do not fit in the governance of the planning team or PA [5].

Most of the PAs, especially National Parks, Biological Reserves, Ecological Stations and National Forests, provide statements of significance in their diagnoses, but these are very comprehensive and are more of a description of the PA than an indication of special elements designated as conservation targets. In these same categories, specific management objectives are usually identified, in some cases together with the researchers who worked on the diagnoses. However, these goals tend to be general and encompass all threatened or special species in the area. Conservation targets and their threats, unusual in Brazilian management plans, should be the basis for the definition of the objectives and results for management of a PA [12–14]. In some countries, such as Costa Rica, Chile, and Argentina, the definition of conservation targets is the first step in the diagnosis. At that moment the information gaps guide the analyses to be carried out are identified [14,33,34].

Classification of PA environments should complement the identification of targets and threats and as a basis for zoning. Among the three possible classifications, state of conservation predominated, likely because it is easier. In general, this is done by analyzing land use and occupation based on vegetation maps, satellite images and deforestation data. Although timber-based assessments allow the identification of areas with different vegetative stages, they do not consider the ecological integrity of environments, which is important for conservation monitoring of PAs [1,5]. Most classifications by biological importance were done using Rapid Ecological Assessments, where researchers regarded the presence of endangered and endemic species. Vulnerability analyses did not show a pattern and were done according to soil fragility and erosion, and with other elements of geology and geomorphology.

One should not neglect future risks and opportunities in diagnoses, especially with climate change, pressure from large enterprises and the advancing deforestation in Brazil [2,16,35], and actions needed to avoid or enhance them [8].

The evaluation of the themes in the diagnoses should be done in an integrated way, to define conservation targets appropriate to the planning. Although there is a trend towards a higher level of diagnosis with the use of methods with primary data collection and long-term research programs, the analyses should be widely performed regardless of the method and amount of information available. Due to scarce resources for conservation, the high cost of data collection in the field and the need for faster and strategic planning in the face of increasing pressures on biodiversity [36]. To improve diagnoses, we recommend integrated analyses with socioeconomic aspects. As ecological aspects are directly influenced by the social context, effective management decisions must consider the socioeconomic dynamics of the PA. Especially in developing countries, where essential management actions, such as land acquisition and protection, are hampered by the scarcity of resources, it is essential to plan based on existing environmental and social information, allocating the few resources available to invest in the analysis of information and adaptive management of PA. Diagnostic analyzes need to be carried out in a better way to achieve a balance between more efficient PMs, which serve as a guide for managers and which are less costly in time and financial resources.

It becomes essential to protect and manage what is not known sufficiently [11], by performing diagnoses and planning of PAs with the best available information, even if it is just secondary data. For this, adaptive management is essential because, as new information and learning are generated, the planning of PAs should be reviewed and improved [8]. One caution about using the best information available to support management is that more conservative measures regarding the use of biodiversity should be prioritized until necessary information is obtained for the safe management of resources. In reserves with communities that depend on resources, investments in research and monitoring should be prioritized. With the recent evidence that assessments of management effectiveness in Brazil do not necessarily reflect conservation results [37,38], the need to improve environmental diagnoses, specially analyses, for planning PAs is even greater. Thus, not only assessments of the effectiveness of PAs for conservation will be facilitated [39], but there will also be gains for biodiversity conservation.

To better connect the diagnoses and the effectiveness of the PAs, MP development should consider: how threats affect species and ecosystems, how these elements are distributed across the territory of PAs and why some actions are needed to mitigate them; use of methods that facilitate the process of analysis, with analysis of causes and consequences of different factors on conservation targets; classification of PA environments should complement previous the analyses above mentioned and provide the basis for zoning; future scenarios should not be neglected in diagnoses considering climate change, development projects and economic and political cycles; different diagnostic topics should be analyzed in an integrated way; the concepts and practices of adaptive management should be the basis of the planning process, including in the diagnostic phase. The absence of these elements leads to the prioritization of MP activities according to the intuition or experience of managers, with ease of execution, or even disregarding indicated recommendations, impairing management.

To avoid the general problem described here, MPs should prioritize data analysis and use of specific management studies. These studies must focus on the use of natural resources, the status of conservation targets, future scenarios and key information to planning. The same diagnostic and planning methods should be used for all categories of PAs in order to reduce discrepancies between levels of diagnosis and planning and, thus, contribute to the management effectiveness of National Protected Areas Systems.