Wetlands cover 1.5–1.6 billion hectares of the Earth’s surface (Davidson and Finlayson, 2019), and harbor 40% of the world’s species (Wetlands International, 2022). Any inland freshwater area, coastal saltwater area (up to 6 m deep) or flooded vegetation, being permanent or temporary, can be considered a wetland (Navid, 1989). Together, these ecosystems host a rich biodiversity and are also responsible for many services for humans, including food and water provision, climate and hydrological regulation, disaster risk reduction, nutrient cycling and primary production (Xu et al., 2020).

However, human action has already caused the loss of 64–71% of global wetlands (Davidson, 2014), mainly due to agriculture and urban expansion (Ballut-Dajud et al., 2022). In addition to being threatened by land use change, wetlands are also sensitive to climatic alterations, which affect the hydrology and drought/flooding regimes of inland wetlands, contributing to their conversion into other ecosystems (Joyce et al., 2016). Despite this, there is limited knowledge on the status and distribution of the world's wetlands (Kingsford et al., 2016). This is even more severe for the Neotropics, given that only 3% of the studies about temporal change in wetland amount were conducted in this biogeographic region (Davidson, 2014).

In response to this wetland decline scenario, in 1971, the Convention on Wetlands of International Importance (hereafter the Ramsar Convention) was created. Although wetlands also have a major importance for people, the initial motivation for the Ramsar Convention was specifically the conservation of habitat for migratory waterbirds (Navid, 1989). In particular, shorebirds, a group of waterbird species of the order Charadriiformes, are reliant on very specific shallow water ecosystems such as tidal flats, river floodplains and flooded grasslands to obtain their food (Burger et al., 1997; Isacch and Martínez, 2003). In coastal areas, shorebirds also depend upon other wetland types, such as mangroves, to rest (hence, roosting habitat) when the high tides are covering their intertidal foraging habitat (Johnston-González and Abril, 2019). In addition, most shorebird species are long-distance migrants that travel across the hemispheres between their temperate breeding grounds and tropical wintering sites (Smith et al., 2023). Therefore, these bird species rely on foraging and roosting habitats distributed across the hemispheres to refuel and rest during their migrations, which makes them particularly sensitive to habitat loss (Pfister et al., 1992; Piersma and Lindström, 2004; Wang et al., 2022). Not surprisingly, shorebird populations have been declining for the past decades, with estimated losses of over 50% of their abundances, signaling high conservation concern (Smith et al., 2023).

About 20% of the Brazilian territory is covered by inland and coastal wetlands (Junk et al., 2014), many of which are critical stopover and wintering habitats for migratory shorebird species of the western hemisphere (Somenzari et al., 2018). However, Brazil only committed to wetland conservation in 1996, when the government enacted the Ramsar Convention in its law (Brasil, 1996). Nevertheless, wetland conservation efforts in Brazil are complex, since the country is one of the largest in the world, with five major geographic regions (South, Southeast, Midwest, Northeast and North) exhibiting different annual precipitation patterns, hydrology and flood-pulsing (Junk et al., 2014) as well as distinct socioeconomic histories and land use patterns (Parras et al., 2024). Such characteristics can directly impact the extent of shorebird habitats in these regions and therefore hinder shorebird conservation. Therefore, understanding the status and distribution of their habitats in Brazil is necessary for shorebird conservation planning – but we still lack a shorebird habitat assessment on a national scale.

In this context, we assessed the spatial and temporal variation in the amount of natural foraging and roosting habitats for shorebirds in Brazil since the implementation of the Ramsar Convention (1996) to the present (2023). Specifically, we evaluated (i) how the area of foraging and roosting habitats varied along the past 28 years between five Brazilian geographic regions, and (ii) which land cover types were the direct cause of the variation (loss and gain) in the extent of these habitats over time within each region. We expected that the amount of foraging and roosting habitats would decline in Brazil, following the global trend of wetlands loss over the past decades (Davidson, 2014), with a more pronounced decline in foraging habitat because inland wetlands are also directly impacted by climatic alterations (Junk et al., 2014). We also expected that changes in habitat extent would vary among Brazilian geographic regions (see more details in Table 1), as each of them have different socioeconomic histories and land use patterns (Parras et al., 2024).

Our findings highlighted that the total amount of shorebird habitats in Brazil showed a slight decrease of about 1% from 1996 (215,113.01 km²) to 2023 (212,525.74 km²). However, we detected a wide variation in the extent of foraging and roosting habitats available for shorebirds over our time series among Brazilian geographic regions (Table 2).

We observed a significant (P < 0.05), yet subtle increase in the area of foraging habitat over the years in the Southeast and Northeast regions, while an opposite and steep pattern was detected in the Midwest region (Table 3, Fig. 2). The foraging habitat gain detected in the Southeast and Northeast regions represents only about 16 and 34 km2/year, respectively. In the Midwest region, however, there was a loss of about 431 km2 of foraging habitat per year. In the South and North regions, the foraging habitat area did not change significantly. Our findings also highlighted a subtle increase in the amount of roosting habitat in the Northeast region (representing 3.5 km2/year), while a significant and slight decrease (3.7 km2 lost per year) was evidenced in the North region (Table 3, Fig. 2). In the South and Southeast regions, the extent of roosting habitat did not change over time.

Fig. 2.

Temporal variation (1996 to 2023) in shorebird foraging and roosting habitat area in the five Brazilian geographic regions. Confidence intervals are shown in gray.

Despite the slight changes in total habitats area, we observed that the amount of foraging habitat that remained unchanged over the past 28 years was only 45.57% in the Midwest, 62.36% in the Southeast, 64.64% in the Northeast, 72.15% in the North and 73.20% in the South. For roosting habitat, the percentage of unchanged area was 50.71% in the South, 73.02% in the Southeast, 83.65% in the North and 86.10% in the Northeast.

Our study also revealed that changes in the amount of foraging and roosting habitats between years are particularly associated with conversions into and from areas of vegetation, agriculture, and water surface (Fig. 3). We observed that habitat loss between years in the South and Southeast regions is associated with the conversion into agricultural areas and vegetation (Fig. 3, Appendix 5). In the other Brazilian regions, the loss of both habitats is related to the increase in water surface and vegetation (Appendix 6). Similar results were observed for the increase of shorebird habitats on areas that were previously other land cover types (Fig. 3, Appendix 5). In the South and Southeast regions, habitat gain was explained mostly by areas of agriculture or vegetation that were replaced by foraging and roosting habitats. For the other regions, vegetation and water surface were the main types of land cover that were replaced by one of the two habitat types (Fig. 3).

Fig. 3.

Amount of foraging and roosting habitats that were either lost (negative values) directly to agriculture, pasture, urban areas, vegetation and water surface or gained (positive values) by conversion from one of these five land cover types, in each of the five Brazilian geographic regions. The habitat area converted to and from the land cover types was calculated per one-year interval and here we show the mean annually converted area and the standard deviation. The letters indicate significant differences (P < 0.05) based on Dunn's test of multiple comparisons (see results in Appendix 5), which was conducted separately for loss and gain.

Our study revealed that the total shorebird habitat amount showed a small decrease since the Ramsar Convention was enacted in Brazil, a pattern that diverges from what has been reported worldwide in recent decades (Davidson, 2014). However, we detected distinct patterns among regions, including a steep decline of foraging habitat in the Midwest, which is consistent with prior knowledge that inland wetlands have experienced greater losses (Davidson, 2014). Although the total habitat area may not have changed extensively in many regions, the spatial location of shorebird foraging and roosting habitats went through consistent changes. Only 45 to 86% of habitats within each region remained constant over time, with the remaining habitat area changing in location throughout the years – that is, within the same region, habitat losses and gains were occurring simultaneously in different sites, in a way that even if the overall habitat area remained roughly the same, the location of such habitats was constantly changing. Most of the changes in spatial location of these habitats were due to conversions into other vegetation types, water surface and agriculture, with the opposite exchange (i.e., vegetation, water surface or agriculture converted into habitat) occurring in other sites within the same region. These results indicated that assessing only the total habitat amount masks important patterns of shorebird habitat change in Brazil and may lead to an erroneous shrinkage of conservation efforts, which can have severe implications to the already declining shorebird populations (Smith et al., 2023).

The slight habitat gain observed in the Southeast and Northeast geographic regions may be related to the implementation of protected areas, which began mostly after 1996. This is consistent with the fact that Brazil only established its national network of protected areas in 2000 (Brasil, 2000). In particular, out of the 238 protected areas that encompass shorebird habitats in 2023, 130 (54.6%) were created after 1996. Another possible explanation for an overall gain particularly in shorebird roosting habitat could be related to recent mangrove restoration initiatives that have taken place in the Northeast (Ferreira and Lacerda, 2016). However, it is important to highlight that the increase in shorebird habitat amount across Brazilian regions was slight (e.g., a minimum gain of 3.5 km2/year for roosting habitat and a maximum of 34 km2/year for foraging habitat, both in the Northeast region), which reflects an overall maintenance of habitat availability over the 28 years evaluated. Nonetheless, this result is already encouraging, considering that global trends indicate a decline in most wetland areas (Davidson, 2014).

In contrast, our study revealed a modest loss of roosting habitat in the North region and a sharp decline in foraging habitat in the Midwest region. Roosting habitat loss in the North region could be linked to sea level rise and consequent changes in coastal vegetation, which has been previously reported (Henriques et al., 2024). Although not apparently alarming, this loss of roosting habitat could affect the population dynamics of already declining and endangered shorebirds, such as Limnodromus griseus, Calidris pusilla and Calidris canutus, which depend on these habitats during the non-breeding season. Conversely, most of the marked loss of foraging habitat in the Midwest region occurred in the Pantanal wetlands, one of the most important stopover sites for shorebirds that migrate through the Midcontinent Flyway (ICMBio, 2023). This result is most likely related to wetland losses caused by reduced precipitation and increased temperatures that the Pantanal has been experiencing in recent decades, which also led to an increase in fires (Silva et al., 2022). Most of the fires affecting natural areas in this region occurred on rural properties, suggesting a likely synergy between land use and climate change (Ferreira Barbosa et al., 2022). This is of particular concern, considering that the globally vulnerable Calidris subruficollis depends on these habitats to rest and refuel during migration. This species has already lost more than 50% of its original population (Smith et al., 2023) and habitat shifting due to climate changes was already assumed to be one of the main drivers of this decline (Lanctot et al., 2009). Therefore, we highlight the urgent need for action in Brazil’s area of the Midcontinent Flyway, especially to increase the extent of protected areas, which currently represents only about 6% of total shorebird habitats in the Midwest region.

Moreover, the high percentage of habitats that have undergone changes over time (i.e., more than 50%) in most regions broadens our concerns about shorebird conservation in Brazil. Many shorebird species, such as Numenius phaeopus and C. canutus (which are both vulnerable in Brazil), are known for their wintering and stopover site fidelity – the birds stop to feed and rest at the same sites during migration and spend the austral summer in the same locations every year (Handmaker et al., 2024; Musmeci et al., 2022), which makes them particularly sensitive to habitat spatial changes. Although the total habitat amount remains roughly the same in many geographic regions, most of the original habitat has been lost, and new habitat areas have formed. If this process occurs within traditional stopover sites of already declining site-faithful species (such as N. phaeopus and C. canutus), they could suffer with increased mortality in the non-breeding season due to lack of high-quality habitats to rest and refuel, therefore continuing their migrations with limiting physiological conditions. In addition, it is difficult to determine whether shorebirds can adapt to these spatial changes and utilize potential new habitats where they lack prior knowledge of local resources. In the Northeast region, about 35% of foraging habitats went through spatial changes. This spatial reconfiguration of habitats in this region can have critical consequences for many shorebird species, because it hosts one site of hemispheric importance (Reentrâncias Maranhenses) that supports 54% of all the Pluvialis squatarola, 72.5% of Arenaria interpres, 49.3% of Tringa semipalmata, and 43.7% of N. phaeopus recorded in South America (WHSRN, 1991), and two sites of regional importance for shorebirds (Bacia Potiguar and Banco dos Cajuais) that hosts more than 1% of the biogeographic population of C. canutus rufa (WHSRN, 2024, 2017) – a threatened species with known site fidelity (Musmeci et al., 2022). Therefore, we stress that it is possible that these recently formed habitats, created through the conversion of other land cover types, do not have the same conservation value to threatened and site-faithful species when compared to sites that already existed and remained unchanged.

Our study also revealed several drivers associated with the high change in the amount and spatial distribution of shorebirds habitats in Brazilian regions. In particular, the main direct cause of both shorebird foraging habitat loss and gain was the conversion to and from areas of vegetation (i.e., foraging habitat was converted to vegetation in some sites within the region, while in other sites vegetation was converted to shorebird foraging habitat), which could be related to changes in the precipitation patterns (Joyce et al., 2016). This result highlights the threat climate change poses to shorebird habitats, particularly inland foraging areas, which are mainly flooded grasslands. These habitats face the dual risk of drying out due to climate change and being converted into other ecosystems (Joyce et al., 2016) that are unsuitable for shorebirds. However, the effects of climate change are not uniform, and some regions of Brazil have experienced increased precipitation, as seen in the South (Dubreuil et al., 2019). In such cases, previously dry grasslands may have been converted into flooded grasslands, leading to a gain in shorebird habitats.

We also observed that the second main cause of foraging habitat change was related to conversion into and from water surface (i.e., foraging habitat was converted into water surface in some sites within the region, while in other sites water surface was converted into shorebird foraging habitat). This result can also be associated with changes in precipitation patterns, once again, because lower water levels in large rivers can expose more floodplains where shorebirds forage (Linscott et al., 2024). However, the loss of foraging habitat due to conversion into water surface could be related to the expansion of hydroelectric dams in Brazil over past decades, especially in the Amazon (Latrubesse et al., 2017). There are currently more than a hundred hydropower dams in the Amazon, with numerous proposals of additional dams (Latrubesse et al., 2017), flooding vast areas of river floodplains where shorebirds once fed during migration.

Regarding roosting habitat, both agriculture and vegetation were the main direct causes of spatial reconfiguration of shorebird habitats across Brazilian regions. Indeed, agricultural expansion has been reported as one of the main causes of mangrove loss worldwide (Ballut-Dajud et al., 2022). In addition, the loss of roosting habitat may be linked to the degradation of vegetation on sandbanks, as human disturbances in the surrounding landscape can facilitate the invasion of exotic grasses in coastal areas (Zamith and Scarano, 2006). In our study, we also detected that the gain in roosting habitat was primarily linked to the direct conversion of other vegetation types and water surface. This result may be associated with restoration efforts, where areas degraded by other vegetation types or lost to aquaculture have been restored and converted back into sandbank vegetation or mangroves (Ferreira and Lacerda, 2016; Zamith and Scarano, 2006).

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Laura Facci Torezan: Conceptualization, Data curation, Methodology, Formal analysis, Writing - original draft, Writing - review & editing. José Carlos Morante-Filho: Conceptualization, Writing - review & editing.