Canga vegetation has high ecological importance in the Serra dos Carajás, southeastern Amazonia, but it coexists with the potential threat of large-scale iron ore mining. Considering Convolvulaceae, this canga environment has only 17 species, and 15 of these species had their pollen grains described in detail in this present work, aiming to contribute to the taxonomic knowledge of critically endangered plants, including Ipomoea cavalcantei. Pollen grains were examined by light and scanning electron microscopy, and the morphological parameters obtained were statistically analyzed using principal component analysis. Therefore, Aniseia cernua was described for the first time in the literature. In general, the echinae morphology were the main differentiating character among the Ipomoea species and was the basis for the proposed pollen key. The family Convolvulaceae in Carajás is eurypalynous, and the genus Ipomoea may be classified as stenopalynous. The set of morphological characters statically treated and correlated was effective for the separation of Ipomoea.

Upland lakes (ULs) of the Carajás, southeastern Amazonia, have been intensively studied to their evolution during the Quaternary, as well as the development of the associated biota. In this review, several classical and modern approaches from structural geology to the pollen rain and sedimentary data which cover an area of around 41,300 km² were compiled. Multi-elemental geochemistry indicates that the detrital sediments derived from weathered crusts and soils, while the sedimentary organic matter represent autochthonous (siliceous sponge spicules, algae, macrophytes) and allochthonous (C3 plants and freshwater DOC) sources. Modern pollen rain suggests that even small lakes and canga areas can reflect forest signal, which depends on the topographic control and prevailing wind direction on pollen deposition. Integrated data of the sedimentary cores indicate that the active lakes never dried up during the last 50 ka cal BP. However, subaerial exposure occurs on filled lakes such as ST02 Lake during the LGM, LB3 and R2 lakes at the mid-Holocene due to drier paleoclimate conditions. Considering the organic proxies, only LB3 Lake presents expansion of C4 canga (montane savanna) plants since ULs of the Serra da Bocaína does not present siderites. Siderite formation on ULs deposits also points to drier paleoenviromental conditions, interrupting predominantly wet conditions. However, there is no evidence for widespread expansion of savanna into Southeastern Amazonia during the late Pleistocene and Holocene.

The pollen content of honey samples collected in the years 2017 and 2019 from experimental apiaries of Melipona seminigra pernigra Moure & Kerr 1950 installed in campo rupestre on canga (CRC) vegetation of the Serra dos Carajás, southeastern Amazonia, was analyzed to understand the local variability of floral resources occurring on natural and disturbed areas. Around one hundred pollen types were identified mainly belonging to Fabaceae, Myrtaceae and Euphorbiaceae (31, 6 and 5 types, respectively). The N5 mine presented the highest pollen richness with 95 pollen types identified, almost twice of those identified in the other areas, including the better preserved ones. Eighty percent of the pollen types are rare with concentrations ≤ 2,000 pollen grains/10 g; the remaining types are the most abundant and frequent, and are considered the primary bee sources (PBS). PBS correspond mostly to native plants such as Tapirira guianensis Aubl., Protium spp., Aparisthmium cordatum (A.Juss.) Baill., Mimosa acutistipula var. ferrea Barneby, Periandra mediterrânea (Vell.) Taub., Miconia spp., Pleroma carajasense K.Rocha, Myrcia splendens (Sw.) DC., Serjania spp. and Solanum crinitum Lam. All pollen types were identified during both seasons, but higher pollen concentration are related to the dry period (June-September). The statistical analysis indicated that there was no significant difference in honey pollen data between the natural and disturbed areas since the plant species considered as PBS in this work are intensively used in revegetation of degraded area (RDA) processes by mining activities.

Remote sensing technologies may play a fundamental role in the environmental assessment of open-cast mining and the accurate quantification of mine land rehabilitation efforts. Here, we developed a systematic geographic object-based image analysis (GEOBIA) approach to map the amount of revegetated area and to quantify the land-use changes in open-cast mines in the Carajás region situated in the eastern Amazon. Based on high-resolution satellite images from 2011 to 2015 from different sensors (GeoEye, WorldView-3 and Ikonos), we quantified forests, cangas (natural metalliferous savanna ecosystems), mine land, revegetated areas and water bodies. Based on the GEOBIA approach, threshold values were established to discriminate land cover classes using spectral bands, and the NDVI and NDWI indices and LiDAR digital ground and slope models. The overall accuracy was higher than 90%, and the Kappa indices varied between 0.82 and 0.88. During the observation period, the mining complex expanded; for that, canga and forest vegetation was converted to mine land. At the same time, the amount of revegetated area increased. Thus, we conclude that our approach is capable of providing consistent information regarding land cover changes in mines, with a special focus on the amount of revegetation necessary to fulfill environmental liabilities.