Humans have depended on coastal reef resources for millennia (Cinner et al., 2018). The dependency and interactions between people and reefs (i.e., economic and cultural) may vary greatly over time, within and among social groups. Certain groups of people may be more dependent on reefs than others, which may also vary through time or seasonally (Costanza, 1999). The interactions between human populations and reefscapes happen through different stakeholders (Marshall et al., 2018), for example, institutional agents responsible for ordering reef use, non-governmental organizations that focus on reef conservation, reef scientists interested in understanding how reefs work, and people that make direct use (extractive or not) of reefs, such as fishers, tourism operators, diving companies, and tourists.

These stakeholders may have different and/or complementary perceptions of the reefs depending on the type and frequency of their use (Eddy et al., 2018). Regular users can pay attention to different characteristics of these environments depending on how they use and access them, which would explain why people have contrasting memories of changes in natural environments (Hicks et al., 2013). For example, there is strong evidence that fishers have detailed knowledge about temporal changes in their target species (Johannes et al., 2000) but do not notice declines in species with less or none economic importance (Damasio et al., 2015). Divers may perceive differences in biological attributes such as fish richness and coral cover, as well as in the structural complexity of coral reefs (Uyarra et al., 2009) and scientists may restrict their perceptions to their particular study target (e.g., fishes or corals).

Reconciling knowledge from different stakeholders, of variable age groups and experiences is an alternative to reconstruct the process of change that a particular species or environment gone through (Hansen et al., 2006). This could be an important tool to reconstruct sensitive reefscapes in areas that lack baseline data and struggle with research funding, management, and enforcement. This is the case of Southwestern Atlantic reefs, most of which are within Brazilian territory, occurring between the latitudes ∼5°N and 27°S and are marked by high species endemism of corals and fishes (Leão et al., 2016; Francini-Filho et al., 2018). These reefs are not homogeneous (Aued et al., 2018), while some of them are similar to typical coral reefs (Northeast region), others consist of rocky reefs that can support coral assemblages (Southeast and South regions; Leão et al., 2003). Brazilian reefs are found in shallow margins close to the coast, island edges and isolated banks (Leão et al., 2003; Kikuchi et al., 2010), many of them are close to densely populated areas where they are more subjected to direct anthropogenic impacts (Moura, 2000; Magris et al., 2021). Brazilian reefs are generally used for both extractive (i.e., fishing) and non-extractive activities (i.e., tourism, recreational diving, and scientific research), and these uses are often more intense when reefs are closer to the shore. Fishing, climate changes and pollution are among the main threats to Brazilian marine biodiversity (Magris et al., 2021), which combined may have caused severe changes in reef biodiversity.

We aimed to understand whether fishers, recreational divers, and reef scientists who use Brazilian reefs have a different perception about potential changes these reefs have undergone and whether they tend to converge or diverge on specific aspects of change. By unraveling, recognizing and connecting these perceptions we may be able to produce a more accurate historical reconstruction of changes and their magnitude in these ecosystems.

This study was conducted between June 2018 and October 2019 in seven states along 3,133 km of the Brazilian coast (Figure 1), an area that comprises more than 50% of the distribution of reefs and diverse reef structures in Northeast and Southeast Brazil (Leão et al., 2016; Aued et al., 2018). The interview procedures were approved by the Ethics Committee at the Federal University of Rio Grande do Norte (CAAE: 73739917.3.0000.5537) and, in the case of protected areas, by the Brazilian System for Authorization and Information on Biodiversity (SISBIO: 65379).

The three groups of stakeholders perceived changes in reef health and pollution, generally agreeing that many species declined in abundance. Because these groups had different perceptions regarding which species have declined or increased, combining their knowledge can help create a more comprehensive understanding of past changes in Southwestern Atlantic reefs. Stakeholders noticed changes in organisms related to their occupations. For instance, fishers mentioned decreases in targeted fishes, such as parrotfish, groupers, sharks and rays, including multiple species that have been overfished and in dire need of management (Giglio et al., 2014; Lessa et al., 2016; Roos et al., 2020). They also indicated a great decrease in shark species within the genus Sphyrna spp. and particularly the species Ginglymostoma cirratum between the 1980s and 1990s (Leduc et al., 2021), and in the locally important black grouper Mycteroperca bonaci (Bender et al., 2014). Parrotfish decline have started in the 1990s, although the exploitation of some species, such as Scarus trispinosus, may have started in the mid-1980s in some parts of the country (Bender et al., 2014). Divers and reef scientists noticed coral declines more frequently than fishers probably because they are more likely to pay attention to the reef substrate and sessile invertebrates due to their recreational and scientific interest, respectively (Giglio et al., 2015). This perception is corroborated by the increase in coral mortality due to more frequent and intense thermal anomalies in addition to land-based stressors in Brazil (Teixeira et al., 2021). Reef scientists were also the only stakeholder group to notice a decline in sea urchin populations. Interestingly, fishers reported an increase in the abundance of black urchins. Sea urchin declines were largely documented in the Atlantic Ocean, such as the emblematic case of Diadema antillarum that almost disappeared after a massive die-off caused by a disease in 1983–1984, which is linked to increased algal abundance in many Caribbean reefs (Hughes, 1994; Tuya et al., 2005). However, such decline noticed by scientists in Brazil probably had little to know effect on sea urchin herbivory since current abundances seem to be enough to control macroalgal in shallow zones of subtropical reefs (Cordeiro et al., 2020). Stakeholders also have different perceptions on which organisms have increased in Southwestern Atlantic reefs. Divers mentioned the increase of organisms in shallow coastal reefs (i.e., Pomacentridae fish, zoanthids, and algae), an area often used by diving companies. Illegal feeding to attract fish and entertain tourists in some of these areas (Silva et al., 2020) may also have affected their perception of increase in abundance. Reef scientists mentioned reef organisms that increased but that were not on the original list (e.g., sponges) and were the only stakeholder group to spontaneously classify a species as invasive. Fishers mentioned an increase in sea turtle abundance more often than any other group of stakeholders, which may be directly related to a fishing ban established in the early 1990’s (Marcovaldi and Marcovaldi, 1999) and to the numerous reports of bycatch in gillnets (Marcovaldi et al., 2006), increasing the contact between fishers and sea turtles. The recovery in sea turtle populations can also be attributed to a massive protection of sea turtle nests in Brazil for over 30 years (Marcovaldi and Chaloupka, 2007). Mentions of new organisms was rare regardless of the stakeholder group, but when it occurred the sun coral Tubastraea spp. was the most cited organism. There is evidence that Tubastraea spp. have been spreading throughout Brazilian reefs, from the states of Ceará (3°S) to Santa Catarina (∼27°S), being a major problem in rocky reefs of Southeastern Brazil (Riul et al., 2013; Capel et al., 2019). Indeed, the sun coral may significantly change the reef community, since experimental competitive interactions between the invasive Tubastraea tagusensis and the native coral Siderastrea stellata caused significant damaged and mortality in the native species (Miranda et al., 2016).

Fishers were generally more pessimistic about the current health state of reefs, which may be related to the decline in stocks of their fishing targets, but also to the fact that they use reefs and the oceans more often than any other user. Divers also classified the current reef health as “bad,” which is likely due to their greater contact with touristic sites, which tend to be more degraded compared to those far from the coast (Hannak et al., 2011). Reef scientists were relatively more optimistic classifying reef health as “intermediate” or “bad.” Although it is not possible to state the reason for this difference in perception among stakeholders, reef scientists use external references from the literature in addition to personal experiences to assess the health status of Brazilian reefs. Therefore, these unified opinions of reef health among scientists may exist because of their education and experience, that could even compensate the shifting baseline because of their formal knowledge (Muldrow et al., 2020). In addition, reef scientists are divers with scientific training and experience, and often interact with fishers or assess information provided by fishers (Bender et al., 2013), which could explain why their perception was mixed with those groups of stakeholder.

Different stakeholders also attributed different threats to the reefs that would help explain their current health status. We only interviewed artisanal fishers and they cited industrial fishing as an important impact on reefs. However, reefs are mainly fished by artisanal fishing, and some of its gear can indeed damage corals (Link et al., 2019) and cause significant impact to fish stocks (Bender et al., 2014). Denying that artisanal fishing activities can have negative consequences to reefs can hinder decision-making (Vaclavikova et al., 2011). For example, fishers may resist management measures, even those aimed at protecting endangered species, if they do not feel at least partially responsible for current reef health. Some fishers also highlighted that impacts on reefs happen for divine reasons, which suggests the difficulty and need to bring scientific information to these groups (Hilborn, 2007). Reef scientists also highlighted the negative impacts of fishing activity on reefs, specifically causing overfishing. Part of these reef scientists may be more aware of the impact of fisheries for being part of groups that assist the government in designing fishing regulations, so they may have access to more detailed fisheries information on a national level. These scientists are invited to these groups exactly for their expertise on the species and awareness of the stock status, these groups facilitate the exchange of information increasing their understanding of fishing impacts.

All groups perceived some level of negative impact of tourism on reefs, which is widely recognized in the literature (Giglio et al., 2017, 2020). Reef scientists are likely to deal with or be aware of impacts caused by tourism such as fish feeding, coral removal, and over-visitation (Liu et al., 2012). Fishers may have a conflict with tourism activities, including competition over space use (Outeiro et al., 2019). Divers may be especially aware of the impact of tourism because they are directly related to this activity (Neto et al., 2017), some of them are tour guides in reef environments and/or have great contact with tourism companies that often give or receive instructions to avoid their impacts on reefs. The fact that some divers understand the impacts of tourism, despite working in or promoting the sector, possibly suggests that they have been following reef degradation in areas increasingly subjected to visitation (Dearden et al., 2007). Conversely, divers can also be critical allies of science and conservation through their involvement in citizen-science programs that suggest divers without previous scientific training can provide reliable estimates of fish abundance (Vieira et al., 2020).

The increase in pollution was also perceived by most stakeholders, although especially by reef scientists and divers, who are more likely to visually notice it in reefs (Costa, 2007). Only divers rated climate change as the most important factor among reef threats. Perhaps divers are more exposed to this type of information through the media and social media than fishers, who tend to have low education levels and poor access to other social services. Divers are also possibly less afraid of expressing an unsupported opinion than reef scientists who do not work on climate-related issues. Scientists are experts in their specialism and expect to be recognized for it, which is probably why scientists do not want to express opinions about subjects outside their expertise (Myers, 2003). In fact, not even the consecutive cases of bleaching observed on the Brazilian coast (Dias and Gondim, 2016; Leão et al., 2019; Ferreira et al., 2021) seem to have been enough to make climate change an important issue to be raised here by reef scientists. A possible factor for this is the lower frequency of thermal anomalies in South Atlantic and particularly low post-bleaching mortality (<5%) when compared to the Pacific and Caribbean until recently (Mies et al., 2020). Climate change may also be difficult to be perceived on its own, especially when it is not easily associated to local climate events (Spence et al., 2011).

Overall, fishers provided more consistent responses. The interviewed fishers were precisely those who target species similar to the fish presented in the questionnaire. Fishers may also be immersed in a more culturally homogeneous world in small coastal communities than that shared by reef scientists and divers from different regions of the country (Reis and D’Incao, 2000). Unlike fishers, reef scientists have their specific interests diffused over a large set of reef species. Compared to the other stakeholder groups, reef scientists provided the least homogeneous responses, sometimes confused with those of fishers, but mainly with those of divers. Although many reef scientists are attentive to interspecific relationships, most are focused on particular groups of organisms and their opinions may only lean toward their research object.

Different stakeholder groups agreed with the changes in reef landscapes, but also share conflicting notions on specific subjects. This disagreement can represent an obstacle to governance and the management of natural resources (Yandle, 2003; Suárez de Vivero et al., 2008), but can also be a source of complementarity as each group perceive unique aspects of changes on ecosystems. Converging information reinforces the idea that some species or certain abiotic characteristics have undergone significant changes that are noticeable by all. By combining these perceptions, we gathered strong evidence that parrotfishes, groupers, sharks, and corals have undergone significant declines, whereas seaweeds, zoanthids and damselfishes have increased in Brazilian reefs. Pollution and fishing are major problems and reef health has suffered and overall decline. Such a scenario may jeopardize not only reef biodiversity but the benefit it provides to many people that depend on it for multiple uses. Combining different knowledge is an important step toward understanding the history of human-caused impacts on ecosystems, mitigating impacts, restoring key ecosystem functions, and preparing for the future.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by the Ethics Committee at the Federal University of Rio Grande do Norte (CAAE: 73739917.3.0000.5537) and Brazilian System for Authorization and Information on Biodiversity (SISBIO: 65379), with the latter specifically for research done in protected areas. Written informed consent for participation was not required for this study in accordance with the National Legislation and the Institutional Requirements.

MQ-A and GL conceived the idea and developed it with PL. MQ-A collected all the data. PL and GL contacted key participants for the interviews. MQ-A and FF performed the statistical analyses. MQ-A and PL wrote the manuscript with inputs from all co-authors and also designed the figures. All authors contributed with text revision and the final format of the manuscript.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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