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Coastal erosion in the changing climate situation is a grievous concern. Global experience varies in this regard due to the variation of the coastal dynamics. Muddy coasts are exceptionally fragile for the welding of the ecological environment, soft sedimentation nature, anthropogenic and natural factors. Therefore, coastal erosion protection is a challenging and daunting task for most of the muddy coasts. Stark pitfalls of the hard structural engineering solution for coastal erosion protection are becoming more prominent. The propensity to adopt nature-based solutions (NbS) for coastal erosion protection, squeeze, and retreat is on the mark, as opposed to grey or engineering solutions. Yet a comprehensive understanding of NbS for coastal protection in the muddy coasts and evidence building from a global perspective is a vacuum. This paper aims to look into the global contexts and experiences of NbSs for coastal protection to provide a cutting-edge analysis of the role of NbS in coastal erosion protection, biodiversity protection, renewing natural habitats, and shielding coastal populations in a changing climate situation. This research uses a systematic review method to explore the global to regional landscape of NbS in coastal erosion, policy framework, and the national experience. The plethora of NbS experience shows the effectiveness in protecting eroding coasts if properly applied in the right conditions under a pragmatic and/or policy-governance approach. Muddy coast in the peri-urban area of littoral countries like Thailand evolves even more critical bio-spheric condition that requires special and urgent attention. The complexity of the muddy coast of the upper Gulf of Thailand has to be critically understood for NbS-driven pivotal pathways to assure sustainable coastal erosion protection and climate-resilient development. • Coastal erosion in the muddy coasts is a grievous concern in the face of climate change. • Protecting coastal erosion is a daunting task as conventional structures are not suitable for fine sediments andexacerbate negative impacts. • Pitfalls of the grey structures necessitate nature-based solutions (NbS) for sediment trap and erosion control. • Global examples of NbS for erosion protection in the muddy coasts are there but not highlighted, overlooked, and less promoted. • The successful implementation of NbS for erosion protection on muddy coasts requires holistic fusion of science, knowledge, skill, and good governance. [ABSTRACT FROM AUTHOR]

Recent observations have heightened concerns that the reduced density of coastal water is leading to a decrease in the frequency of basin water renewal in Norwegian sill fjords. There are indications that coastal water is becoming lighter due to climate change. The renewal of fjord basin water constitutes the primary source of oxygenation in these fjords, and many sill fjords naturally undergo stagnation periods lasting up to several years. In this paper, we have mapped alterations in coastal water using time series data from hydrographic measurements along the coastline, utilizing them as input for a simplified two-layer fjord model. We demonstrate that the temperature has risen, salinity has decreased, and consequently, the density of coastal water has declined since approximately 1990. At a depth of 10 m, the rise in temperature and the reduction in salinity made similar contributions to the decrease in density. However, at depths of 50 and 100 m, the increasing temperature emerged as the primary factor. The density exhibited a more substantial decrease in the upper layers compared to the lower layers. Consequently, not only was the water less dense, but the stability of the water column had also increased. The estimated temperature in the fjord basins increased after 1990 in 98 out of 101 evaluated fjords, with an average increase of 0.6 °C. The altered coastal stratification had an impact on the estimated work against the buoyant forces in the fjord basins. In 78 out of the 101 fjords, the work against buoyant forces by diapycnal mixing increased. In most of the fjord basins where the work against buoyant forces increased, the rise was insufficient to compensate for the decreasing density at the coast. Consequently, basin water renewal occurred less frequently in 65 out of the 101 fjord basins along the Norwegian coast. • Coastal monitoring in Norway show altered coastal climate since 1930. • The Norwegian coastal water has decreased in density. • The stratification along the Norwegian coast is intensified. • Both coastal water and fjord basin got warmer after 1990. • Water exchange in fjord basins occure less frequent than before. [ABSTRACT FROM AUTHOR]