Pollen analysis

Climate change is projected to alter species' natural distribution and reduce ecosystem biodiversity. Hence, understanding the dynamics of vegetation distribution concerning palaeoclimate change is essential for a sound forecasting of the response of vegetation to future climate change. The distribution and abundance of pollen taxa reflect, on a regional scale, spatial variations in the composition of plant communities and biomes. This, in turn, provides information on the prevailing macroclimate. Hence, if the network of well-dated pollen records in a particular area is large enough, the data can be analysed and mapped to show changing distributions and abundances of individual taxa, changing spatial patterns in reconstructed vegetation and broad-scale variations in the paleoclimate.  Here, we study fossil-pollen records in combination with Species Distribution Models (SDM) for hindcasting the Quaternary forest refugia from the Last Glacial Maximum (LGM) to the present. SDM and paleo records are interrelated and offer intriguing new insights for future projections of vegetation dynamics under the anticipated global warming and climate change scenarios. Combining these two approaches would enable better accuracy of SDM applications in predicting potential Quaternary forest distribution. In addition, the modelling results would help to identify environmental variables affecting the diversity and distribution of plant communities and aid in formulating its conservation strategies. 

Mangroves inhabit the intertidal zones in tropical and subtropical regions and monitor the exchange of matter at the interfaces of the terrestrial, marine and atmospheric ecosystem. This specialized ecosystem offers several ecosystem services, like alleviating coastal erosion by wind and waves, ensuring fishery resources and food security for coastal population, and protecting the coastal biodiversity. Mangrove ecosystem is notably an effective producer as well as a sink of carbon. Therefore, it plays a key role in global carbon cycling, and is an important blue carbon sink that can contribute to climate change mitigation. However, mangroves are highly vulnerable to climate change and fluctuations in relative sea level. They can migrate landward/seaward with the rise/fall in the relative sea level (RSL). A rapid change in the RSL can lead to a decline or disappearance of mangrove habitats. Similarly, low intensity precipitation also results to mangrove degradation through reduction in freshwater runoff, fluvial sediment, and nutrient input. Extreme warming events result in hypersaline conditions with high evaporation rates, which also cause mangrove forest degradation. The world at present is facing rapid sea level changes, frequent extreme climatic events, and an increasing population. Hence, reconstruction of past mangrove responses through climate indicators recorded in sediments is crucial to predict the fate of mangrove ecosystem under the influence of rapidly changing environment. Palynological succession of estuarine formations due to their situation along the coasts, are constantly controlled by marine and terrestrial factors such as, coastal erosion or accretion by the sea or by rivers, tidal waves, high salinity, water-logged soils and other edaphic characteristics. These, together with the distance from the sea, the frequency and duration of inundation and tidal dynamics, govern the distribution of mangrove species and their succession. 

Mangrove taxa are segregated or zoned on the basis of their specific requirements such as tidal amplitude, salinity of water, soil salinity range and aeration of the soil. Mangroves possess water buoyant propagules which can be dispersed by estuarine current, wind, wave, tides and ocean circulation that helps in long distance transport and maintain their high diversity in the warm tropical intertidal belt. Due to their habitat specificity, mangroves expand or contract according to change in the climatic conditions and sea level fluctuations. Mangroves possess fossil records extending back to the Cretaceous era, 100 Ma providing the evidence of its global disjunct distribution. Mangroves occur in two distinct biogeographical regions: the Indo-West Pacific (IWP), which includes Asia, Australia, Oceana and the eastern coast of Africa; and the Atlantic East pacific (AEP) region, which covers the Americas and the western coast of Africa. Except for the Rhizophora mangrove which is cosmopolitan, the tropical zone of the  Indo-West Pacific (IWP) and Atlantic East Pacific (AEP) regions display different mangrove genera suggesting the Pacific Ocean forming a key biogeographic barrier for the distribution of mangroves. In order to determine whether mangroves were ancestral plants of unique ecology or they got derived from other land plants, it is necessary to trace the origin of mangrove taxa in geological records.