Nature-Based Solutions: Mitigating Flood Effects on Forest Tree Biodiversity and Societal Factors

Abstract

Nature-based solutions (NBS) are effective measures to deal with climatic hazards like flooding, droughts, landslides, and other global sustainable development challenges. But study regarding this is limited in Nepal. Therefore, this study was objectively constructed to assess the effects of flood on forest tree biodiversity and social features as well as spatial dynamics of nature-based solutions. Study site was taken from three community forests named as Marka Urra, Kalikhola and Bhaunijhora of Mahottari districts. Total 90 plots were established in CF. To collect the social data, 5 key informant interviews, 3 focus group discussion and 90 household survey including photograph and coordinates were abstracted through GPS. The study mainly focuses on how the implementation of NBS in the three different community forests near the Ratu River, has minimized the effects of floods. For the comparison study the site was categorized into affected and non-affected site. The study indicated that even though flooding occurrences are frequent, the consequences of floods in the communities and forest areas were lessened after the implementation of NBS. The species evenness and richness for trees and poles were found similar. Which indicates that, floods do not affect trees and poles but saplings and seedlings. The result showed    that the variation in rainfall patterns was analyzed from the years 2009–2021. The highest rainfall was recorded 2142 mm in 2021. In 2020, rainfall with a value of 1897.52 mm was recorded. With 17 total rainy days, in 2013 the lowest amount of precipitation i.e., 355.3 mm was received. At affected sites highest and lowest average Shannon diversity of saplings and seedlings were 0.84±0.07, 0.75±0.10; 1.20±0.08, 0.67±0.09 respectively. Species evenness were 0.28±0.03, 0.25±0.03; 0.34±0.01, 0.30±0.04 respectively and richness were 2.5±0.20, 2.2±0.25, 3.5±0.29, 2.33±0.21. Similarly, The Shannon diversity of saplings and seedlings were 1.15±0.08, 1.05±0.05; 1.103±0.07, 0.9±0.03 respectively. Species evenness were 0.26±0.07, 0.23±0.04; 0.23±0.06, 0.2±0.05 respectively and richness were 4.64±0.29, 4.41±0.32; 4.76±0.32, 4.32±0.23 respectively. The highest values of IVI for trees, poles, saplings and seedlings were 218.14, 232.06, 44.26 and 28.16 (Shorea robusta) respectively. Similarly, lowest values were 212.02 (Shorea robusta), 215.93 (Shorea robusta), 1.33 (Acasia catechu) and 0.98 (Bidens pilosa and Elusine indica) respectively. The extent and magnitude of flood events is in increasing, the loss and damage caused by the floods in infrastructures, lives, agriculture, forestry and other sectors have been increasing. The NBS adapted in this CF are tree plantation and hedges, bamboo fencing, dyke, dam, and gabion wall. This study will be useful to understand the knowledge about the nature base solution in the community forests.