**2. River basin conservation under changing climate**

The river basin conservation can be achieved if every activity is carried out based on the principle of sustainability that combines a balance between productivity and conservation to achieve the river basin management goal of improving water management; improving soils; controlling land degradation processes; increasing farmers' income; and encouraging the community towards conservation activities that control runoff and flooding [12].

Broadly speaking, the river basin system can be divided into three parts, namely upstream, middle, and downstream. The upstream river basin ecosystem is very important in the river basin system because it functions as an overall river basin protection system. The upstream area is characterized as a rural ecosystem with four main components, namely: villages, cropland, rivers, and forests. Thus, upstream

river basin management is not only to maintain the river basin function but also to improve livelihoods and improve the economy of local communities sustainably [13]. It emphasizes that the balance between meeting the needs of local communities and preserving natural resources is a prerequisite for achieving the goals of sustainable river basin management. The strategy that is seen as an approach to community participation in river basin management in community-based natural resource management is known as Community-Based Natural Resource Management. This approach began to develop in the late 1990s, along with the passing of the era of decentralization and democracy.

The rapid increase in population and economic development activities in the river basin causes changes in land use and very high use of fossil fuels. These two activities are the largest sources of greenhouse gas (GHG) emissions in the river basin. The continuous increase in GHG emissions causes global warming, which affects the climate in the river basin.

Global GHG emissions are projected to peak between 2020 and at the latest before 2025 in global modeled pathways that limit warming to 1.5°C (>50%) with no or limited overshoot and in those that limit warming to 2°C (>67%) and assume immediate action [14]. Global warming is a problem that humans must face now and is no longer a future problem. This event impacts the long-term accumulation of atmospheric pollution due to human activities, causing the release of GHG into the atmosphere at a very high rate which then impacts climate and the environment. Climatic events such as floods, long droughts, and strong winds have been happening more frequently lately with high intensity [15]. This incident is increasingly causing a greater impact with the high level of environmental damage.

Global warming caused by GHG has affected the world's climate. IPCC (2001) in Climate change 2001: Impacts, Adaptation, and Vulnerability: Contribution of Working Group II to the third assessment report of the 74 Intergovernmental Panel on Climate Change states that climate change refers to the variation in the average climatic conditions of a place or its statistically significant variability over a long period of time, at least 30 years. It is further said that over the last 100 years (1906- 2005), the earth's average surface temperature has risen by about 0.74°C, with greater warming on land than in the oceans.

Climate change has positive and negative impacts on all sectors of human life. However, most of the impacts are negative. To assess the impacts of climate change, it is necessary to estimate how the climate is changing at local and regional levels and how these changes affect ecosystems and human life. Most scientists use Global Circulation Models (GCMs). GCMs have been used to assess the impact of climate change on all sectors of life in Indonesia.

Climate change, especially temperature and rainfall, causes changes in discharge fluctuations in the river basin. For example, in Indonesia, it shows an increase in temperature of around 0.1o C–0.5o C in 2010 and in 2070 around 0.4<sup>o</sup> C–3.0o C, while globally there is an increase in temperature between 0.6<sup>o</sup> C–1.7o C by 2030 and 1.0o C– 1.7o C by 2070. Naylor et al. have projected that until 2050 April, May, and June, there will be an increase in rainfall in Central Java, while in July, August, and September, the conditions are projected to be extraordinarily dry [16].

Changes in debit fluctuations in the river basin that are getting higher greatly affect the lives of people in the river basin. Sensitive communities will respond to this condition and cause an increase in community vulnerability in the river basin. However, people who have the ability to adapt will survive with changes or hydrological conditions in this river basin. The sensitivity and adaptability of the community

can be assessed from five aspects of life, namely: physical/technology, social/institutional, economic, human resources, and nature.

The level of community vulnerability is influenced by the amount of exposure, the sensitivity of the community, and the adaptability of the community. The higher the exposure and sensitivity of the community, the higher the level of community vulnerability will be. Meanwhile, the higher the adaptability, the lower the level of community vulnerability. In other words, the level of vulnerability is a positive function of community exposure and sensitivity and a negative function of the community's adaptive capacity.

The impact of climate change will occur slowly and continuously. Therefore, adaptation to climate change is very important. One of them is using nature, especially River Basin ecosystems, as one of the adaptation strategies to climate change. River Basin is an area bounded by a ridge that drains water from upstream to downstream. The river basin is divided into upstream, middle, and downstream areas, so the river basin has the function of regulating the hydrological, economic, ecological, and social aspects of an ecosystem.

Based on the results of a search on the International Disaster Database, 345 natural disasters fall into the global disaster category. Around 60% of these disasters are natural disasters due to extreme climate events such as floods, droughts, forest fires, strong winds/storms, landslides, high tidal waves, and outbreaks of disease [15]. This finding is in line with the results of a study by the Intergovernmental Panel on Climate Change [17] that global warming will increase the frequency and intensity of extreme climate events.

For example, extreme climate events in Indonesia are often associated with the El Niño Southern Oscillation (ENSO) phenomenon. There is a strong correlation between ENSO incidence and rainfall variability in Indonesia, namely long dry spells in El Niño years and far above normal rainfall in La Niña years [15]. Global warming will impact increasing the incidence of droughts and floods. Besides that, the beginning of the season and the length of the season will also shift.

Naylor et al. found an effect of global warming on seasonal changes in Java. Their research showed that areas south of the equator would experience a decrease in rainfall while those north of the equator will experience an increase in rainfall. The results of the projections of Naylor et al. showed that in the next 40 years, global warming would cause the beginning of the rainy season in Central Java to experience a setback with rainfall that tends to fall, while the end of the rainy season will be faster with rainfall that tends to increase. This has implications for the increasing risk of drought in the dry season and the risk of flooding or landslides in the rainy season. WWF Annual Review 2007: A watershed year states that the change in the distribution of rainfall causes various potential natural disasters triggered by rainfall to become higher, such as floods, landslides, overflowing rivers, and the spread of disease vectors, while in conditions of reduced rainfall, potential disasters such as drought, crop failure, lack of clean water, and various social problems that may arise.

River Basins provide natural resources that offer many benefits to the surrounding population, including agricultural resources, clean water sources, freshwater fisheries resources, and other water uses. Various community activities along the river basin affect the quality and quantity of the river basin. In addition, the issue of climate change has exacerbated the condition of the River Basin. The increase in temperature and rainfall affects the hydrological conditions of the River Basin.

River Basin degradation causes ecosystems to not optimally provide functions and services that are very important for human life. This condition causes a decrease in

the level of community welfare and increases the level of community vulnerability. Community vulnerability is a condition of society that cannot adapt to changes in the ecosystem caused by a certain threat [18]. Vulnerability is a function of three components: exposure, sensitivity, and adaptive capacity (IPCC 2001). The main impact of climate change is the level of community welfare in the upstream, middle and downstream areas.

The shift of seasons in the River Basin area impacts agricultural activities by the community. Agriculture that relies on water supply from the River Basin is done in an ineffective and unprofitable way. The unpredictable climate is also one of the reasons the rice fields are not productive. Water production at some points decreased and even disappeared. The number of dangerous and vulnerable areas has increased. Landslides have increased in the last 2 years [15]. The increasingly critical upstream River Basin degradation causes the River Basin not optimally to provide its functions and services for the community. Upstream River Basins as buffer zones, water catchments, sources of water filters, and carbon sinks will be damaged. Consequently, it will lose water supply and in the rainy season will result in flooding. In a matter of years, this region will become critical. Sensitive people will be more vulnerable, while people who can adapt will survive. Based on these conditions, it is necessary to study the level of community vulnerability to climate change in the upstream River Basin. The existence of climate change and River Basin damage that occurs in the upstream River Basin requires an adaptation strategy. River Basin-based adaptation strategies are important considering that River Basins are providers of ecosystem services for the sustainability of upstream River Basin functions.
