Evolution of Asian drying since 30 Ma revealed by clay minerals record in the West Pacific and its tectonic-climatic forcing

As the second largest dust source on the globe,the tectonic and climatic evolution of continental Asia has an important impact on regional and global climate change.The West Pacific is the main sediment sink for eolian dust transported eastward from the Asian interior.Clay minerals,as the major fine-grained weathering products of continental rocks,can be readily transported by wind or currents over long distances and thus have been widely used in the reconstruction of paleoclimate and weathering history.However,the overall evolutionary tendency and response mechanism of clay mineral records over large spatial and long timescales across Asia remain unclear.Here,two continuous and high-resolution clay mineral records since 30 Ma were reconstructed from sediments at Deep Sea Drilling Program(DSDP)Sites 292 and 296 in the Philippine Sea.Clay minerals and Sr-Nd isotope compositions were used to constrain provenance and reconstruct the drying history of the dust source region since the Oligocene.The results show that the clay-sized detrital sediments in the Philippine Sea are a mixture of Asian eolian dust and volcanic materials from the West Pacific arcs.Based on the clay mineral compositions and eolian flux,we reveal that the Asian interior has been continuously drying since the late Oligocene and that stepwise enhanced aridification occurred at approximately 20,14,7,and 3 Ma.Compared with other regions of the world,the relative contents of illite and chlorite increased more dramatically in Asia during the late Cenozoic,and the inconsistency became more obvious at approximately 20 Ma.Since 3 Ma,illite and chlorite have increased consistently across the globe.Combined with the Asian tectonic and climatic history,we suggest that the increase in illite and chlorite from Asia between 20 and 3 Ma was mainly in response to the uplift of the Himalayan-Tibetan Plateau,whereas after 3 Ma,it was primarily controlled by global cooling driven by the expansion of the Arctic ice sheet.

Globally Important Agricultural Heritage Systems(GIAHS)of China:the challenge of complexity in research

The challenge of researching Globally Important Agricultural Heritage Systems(GIAHS)as complex systems forms the subject matter of this study.Complex adaptive systems are those that combine natural ecological processes with human interactions to produce a mutually supportive agro-ecological system.In China,these highly varied systems have the added dimension of long historical time,in that they have evolved over many centuries and thus add a historical dimension to the natural and human dimensions of complexity.In preparing research on GIAHS,it is clear that seeing GIAHS sites as whole systems is an essential starting and ending point.Examining the adaptive capacity of a GIAHS with its multiple scales and complex interdependencies is a major challenge for researchers accustomed to specialized disciplinary thinking.A GIAHS represents a mature agro-ecological system with human agency as a central component that has been honed over many centuries,and has already adapted to many perturbations and changes.The beauty of the GIAHS is in the integration of custom,knowledge,and practice,and it should be studied for its"wholeness"as well as for its resilience and capacity for"self organization."The agro-ecological approach opens the possibility of researching a system as a whole and of taking its complexity seriously.This study reviews the essential features of the GIAHS as a complex adaptive system where uncertainty is normal and surprise is welcome and,in a case study of Qingtian rice–fish culture system,focuses on new perturbations,namely loss of young people and the introduction of tourism.