Browsing by Author "de Nascimento, Lea"
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- 14,000 years of climatic and anthropogenic change in the Afromontane forest of São Tomé Island, Gulf of GuineaPublication . Castilla-Beltrán, Alvaro; F. De Lima, Ricardo; Benitez Bosco, Laura; Castillo Armas, Rosa Delia; Strandberg, Nichola; Stévart, Tariq; de Nascimento, Lea; Fernández-Palacios, José María; Nogué, SandraSão Tomé (Gulf of Guinea, Central Africa) is a 854 km2 tropical island that had a pivotal role in early European colonial expansion through the Atlantic between the 15th and 16th centuries. Historical sources suggest that native vegetation has been heavily impacted since human arrival (1470 CE) due to monoculture economies and the introduction of mammals and plants, some of which now have established wild populations. The Afromontane forest of São Tomé, located above 800 m.a.sl., is particularly rich in endemic plant species and has remained relatively unaffected by direct human impacts. Here, we explore how environmental change influenced this forest through the study of a sedimentary sequence from the volcanic crater of Lagoa Amélia (1340 m a.s.l.), a palustrine system located at the boundary between submontane (800–1400 m a.s.l.) and mist forest (above 1400 m a.s.l.). We used fossil pollen, non-pollen palynomorphs, sedimentology and charcoal to determine forest dynamics from the Late Pleistocene to the present. From 14,000 to 12,500 cal yr BP the forest was dominated by taxa from higher altitudes, adapted to cooler and drier climates (e.g. Afrocarpus mannii trees and Psychotria nubicola). After 12,500 cal yr BP, a potential uphill migration was identified by an increase in taxa like the trees Symphonia globulifera and Craterispermum cerinanthum. From 11,200 cal yr BP through the rest of the Holocene taxa from lower altitudes became dominant (e.g. Prunus africana, Polyscias, and Sabicea), except at c. 8500 cal yr BP when rapid cooling led to forest opening. Charcoal showed that fires were frequent during the Late Pleistocene (14,000 to 11,200 cal yr BP), becoming rare during the Holocene until anthropogenic fires started at c. 220 cal yr BP. Other recent anthropogenic impacts detected in Lagoa Amélia included the appearance of pollen of introduced plant species (e.g., Cestrum), and the increase in pollen of economically important species (Elaeis guineensis, Zea mays) and in fungal spores related to introduced herbivores. Our results reveal that climate changed the altitudinal distribution of the Afromontane forest in São Tomé during the Late Pleistocene, as observed on the African continent, and that this ecosystem was also strongly impacted by human arrival, through fire, farming, and introduced species.
- Global change in microcosms: Environmental and societal predictors of land cover change on the Atlantic Ocean IslandsPublication . Norder, Sietze J.; F. De Lima, Ricardo; de Nascimento, Lea; Lim, Jun Y.; Fernández-Palacios, José María; Romeiras, Maria M.; Elias, Rui B.; Cabezas, Francisco J.; Catarino, Luís; Ceríaco, Luis M.P.; Castilla-Beltrán, Alvaro; Gabriel, Rosalina; de Sequeira, Miguel Menezes; Rijsdijk, Kenneth F.; Nogué, Sandra; Kissling, W. Daniel; van Loon, E. Emiel; Hall, Marcus; Matos, Margarida; Borges, P.A.V.Islands contribute enormously to global biodiversity, but their species and ecosystems are highly threatened and often confined to small patches of remaining native vegetation. Islands are thus ideal microcosms to study the local dimensions of global change. While human activities have drastically transformed most islands, the extent to which societal and environmental conditions shape differences in land cover remains unclear. This study analyses the role of contrasting environmental and societal conditions in affecting the extent of native vegetation cover on 30 islands in five Atlantic Ocean archipelagos (Azores, Madeira, Canary Islands, Cape Verde, Gulf of Guinea Islands). We adopt a mixed-method approach in which we combine a statistical analysis of environmental and societal variables with a qualitative reconstruction of historical socioeconomic trends. Statistical results indicate that terrain ruggedness predominantly shapes the extent of remaining native vegetation cover, suggesting that topography constrains human impacts on biodiversity. Overall, environmental variables better explain differences in native vegetation cover between islands than societal variables like human population density. However, throughout history, islands experienced large changes in demography and socioeconomic trends, and therefore modern patterns of native vegetation might also partly reflect these past conditions. While anthropocene narratives often present humans as a global geophysical force, the results show that local environmental context strongly mitigated the degree of human impact on biodiversity. These findings call for integrative approaches to understand the contributions of local human-environment interactions to ongoing global change.
- In defence of the entity of Macaronesia as a biogeographical regionPublication . Fernández‐Palacios, José María; Otto, Rüdiger; Capelo, Jorge; Caujapé‐Castells, Juli; de Nascimento, Lea; Duarte, Maria Cristina; Elias, Rui B.; García‐Verdugo, Carlos; Menezes de Sequeira, Miguel; Médail, Frédéric; Naranjo‐Cigala, Agustín; Patiño, Jairo; Price, Jonathan; Romeiras, Maria M.; Sánchez‐Pinto, Lázaro; Whittaker, Robert J.Since its coinage ca. 1850 AD by Philip Barker Webb, the biogeographical region of Macaronesia, consisting of theNorth Atlantic volcanic archipelagos of the Azores, Madeira with the tiny Selvagens, the Canaries and Cabo Verde, andfor some authors different continental coastal strips, has been under dispute. Herein, after a brief introduction on the termi-nology and purpose of regionalism, we recover the origins of the Macaronesia name, concept and geographical adscription,as well as its biogeographical implications and how different authors have positioned themselves, using distinct terrestrial ormarine floristic and/or faunistic taxa distributions and relationships for accepting or rejecting the existence of this biogeographical region. Four main issues related to Macaronesia are thoroughly discussed: (i) its independence from theMediterranean phytogeographical region; (ii) discrepancies according to different taxa analysed; (iii) its geographical limitsand the role of the continental enclave(s), and, (iv) the validity of the phytogeographical region level. We conclude that Macaro-nesia has its own identity and a sound phytogeographical foundation, and that this is mainly based on three different floristic com-ponents that are shared by the Macaronesian core (Madeira and the Canaries) and the outermost archipelagos (Azores and CaboVerde). These floristic components are: (i) the Palaeotropical-Tethyan Geoflora, formerly much more widely distributed inEurope and North Africa and currently restricted to the three northern archipelagos (the Azores, Madeira and the Canaries);(ii) the African Rand Flora, still extant in the coastal margins of Africa and Arabia, and present in the southern archipelagos(Madeira, the Canaries and Cabo Verde), and (iii) the Macaronesian neoendemic floristic component, represented in all thearchipelagos, a result of allopatric diversification promoted by isolation of Mediterranean ancestors that manage to colonizeCentral Macaronesia and, from there, the outer archipelagos. Finally, a differentiating floristic component recently colonizedthe different archipelagos from the nearest continental coast, providing them with different biogeographic flavours.
- Oceanic Island forests buried by Holocene (Meghalayan) explosive eruptions: palaeobiodiversity in pre-anthropic volcanic charcoal from Faial Island (Azores, Portugal) and its palaeoecological implicationsPublication . Góis-Marques, Carlos A.; Rubiales, Jose M.; de Nascimento, Lea; Menezes de Sequeira, Miguel; Fernández-Palacios, Jose Maria; Madeira, JoséIn Faial Island (Azores Archipelago, North Atlantic Ocean), charcoalified and mummified wood fossils have been reported within late Holocene (Meghalayan) pyroclastic deposits from the Caldeira Formation. Due to their recent age, a detailed study conveys a snapshot into Azorean palaeophytodiversity and palaeovegetation, ca. 7–5 centuries before the arrival of Portuguese settlers to the Azores Islands. Here we provide the first detailed anatomical and taxonomical study of these wood fossils. In total, 41 samples were collected from seven localities, mainly from a ~1200 yr BP ignimbrite. Field work revealed autochthonous and paraautochthonous assemblages, with tree trunks in upright position. The anatomical study of the fossil woods resulted in the identification of Juniperus brevifolia, Laurus azorica, Myrsine retusa, Morella faya, Picconia azorica, Prunus lusitanica subsp. azorica, and Vaccinium cylindraceum. Two fossil assemblages are comparable to the proposed potential natural vegetation (PNV) for the Azores. Surprisingly, P. lusitanica subsp. azorica was the second most abundant fossil wood suggesting that this tree was more abundant in a recent past in Faial Island and probably in the archipelago. This is corroborated by historical accounts, and its modern scarcity was certainly anthropically driven. Identifying Holocene plant macrofossils is essential to properly reconstruct oceanic islands terrestrial palaeoecosystems, especially where forests with high percentage of entomophilous taxa are underrepresented in palaeopalynological limnic record. Further work is necessary to reconstruct Faial Island and Azores archipelago palaeovegetation which is essential to provide an ecosystem base-line for restoration and management.