**1. Introduction**

The overwhelming global effects of climate change and its implications subtle changes in the earth's orbit belongs long term and immediate impacts. The impacts on atmosphere, ecosystem and sea as a consequences of human activities, warming globe, raising air and sea temperature dropping by 0.01 °C every 100 years for the last 7,000 years and since 1970 the temperature has been rising at an alarming rate of 1.7 °C per century. Consequently, IPCC efforts recommended limit global temperatures below 1.5 °C to avoid the more severe impacts of global warming [1].

The warmer temperature due to climate change increases frequency of ground level ozone, lethal air pollutants, and smog components [2]. Both the immediate impacts of climate change regards extreme weather, heat waves, storms, and flooding, forest fire, compromised safety, economic challenges and long-term effects likewise on human health, ecosystem, threats on water and food resources, altitudinal and tree line shifting are the consequences of climatic change issues today. The pragmatic climate change effects sensed on environment globally comprises shrinking glaciers, shifted plants and animals ranges and sooner tree flowering, loss of sea ice, enhanced sea level rise, penetrating heat waves affecting our dependency upon water, energy, terrestrial and aquatic ecosystems, agriculture, and human health. The future prediction of climate change has great challenge to preserve existing ecosystem and biodiversity. The projections showed 10% approximate species to be an increasingly high risk of extinction for every 1 °C rise in global mean temperature, within the range of future scenarios modelled in impacts assessments (typically <5 °C global temperature rise) as per IPCC AR4. The vulnerable ecosystems are freshwater habitat and wetlands, arctic and alpine ecosystems, cloud forests, mangroves, coral reefs to the impacts of climate change.

The impacts of climate change has extremely affected human societies and the natural environment. The most vulnerable to climate change impacts on an ecosystems area associated with the shifting alpine ecosystem to higher elevations and shrink in area, modification on tropical and subtropical rainforests, affected coastal wetlands by sea-level rise and saline intrusion, affected inland ecosystems by changed rainfall patterns and affected tropical savannahs by changes in the frequency and severity of bushfires. According to Dolling et al. [3]; Giambelluca et al. [4]; Frazier et al. [5]; increased drought stress of native plants and fire occurrence is due to decreasing rainfall and increasing temperatures. According to the IPCC 5th Assessment (IPCC 2013) [6], ocean surface temperature and combined land and warming globally was around 0.85 [0.65 to 1.06] °C, over the period 1880 to 2012. The issue of climate change have created by human activities is about 1 °C of global warming above pre-industrial levels with range of 0.8° to 1.2 °C [7]. The large influence on forest and agricultural systems due to increases in temperature, changes in precipitation patterns, and changes in the occurrence of floods and droughts has predicted by the Álvaro-Fuentes et al. [8]; Anaya-Romero et al. [9]; Conant et al. [10]; Lal [11]; Muñoz-Rojas et al. [12].

As an important environmental factor, climate influence ecosystems and biodiversity several ways whereas climate change affects habitats of species and existing food chain interacting other human stressors like development. The stressors cause minor and major affects including dramatic ecological changes some of their cumulative impacts [13]. Due to changes in the timing of seasonal life cycle, many species influences their migration, blooming and reproduction including reduced their growth and survival [14, 15]. The habitat range of the species both terrestrial and aquatic environment shift to higher elevations due to increased temperatures including changes in vegetative biomes [16] and expanding into areas of river and streams previously inhabited by Coldwater species [17]. Similarly, particular species can ripple through a food web and affect a wide range of other organisms as the loss of sea ice affected entire food web, from algae and plankton to fish to mammals [18]. The extreme events like wildfires, flooding, and drought serves ecosystems as natural buffers and human modification restrict ecosystems' aptitude to temper the impacts of extreme conditions which increases vulnerability to damage. Likewise, the main stressors of climate change like habitat destruction and pollution subsidize to species extinction and spread of pathogens, parasites, and diseases, with potentially serious effects on human health, agriculture, and fisheries. Thus, the species extinction rate globally is exceeding the observed natural rate of extinction [19].

In Nepal, the major driving force to degrade biodiversity and ecosystem is development of infrastructures such as construction of road, hydropower, irrigation canal, railway, transmission line, tourism industry and airport. The accelerated impacts of these activities allies with deforestation and degradation of natural forests, habitat fragmentation, infrastructure development on protected areas, encroachment of forest and forest land, destruction of natural habitats both terrestrial and aquatic species. The urbanization and population growth leads to unplanned infrastructure development ultimately has increased demand of natural products, and pressure on biological resources threatening natural ecosystem and biodiversity.

The rainfall patterns and temperature regimes altered by the climate change and its impacts on water, agriculture and biological resources are crucial issues in Nepal. The policy of the government in biodiversity conservation and economic development is ineffective for implementation integrating the development actions. An effective implementation of regulatory framework and strategy to protect biological resources including protected, endangered, threatened, rare and endemic species can support to conserve the biodiversity and ecosystem. Thus, the chapter assisted overall climate change scenario describing impacts and implications, focusing on ecosystem and biodiversity, including impacts of developmental projects, adoption of national mitigation strategy and use of assessment tools with Nepal's perspective.
