Razali et al. Ecological Processes (2018) 7:19 https://doi.org/10.1186/s13717-018-0126-8 REVIEW Open Access Land use change in highland area and its impact on river water quality: a review of case studies in Malaysia Azlini Razali1, Sharifah Norkhadijah Syed Ismail1*, Suriyani Awang2, Sarva Mangala Praveena1 and Emilia Zainal Abidin1 Abstract The policy of encouraging agriculture and development for mass tourism has led to environmental problems in Cameron Highlands, Malaysia. Rampant development and land clearing have significantly altered the land cover of Cameron Highlands for the past 30 years. Sensitive highlands areas are prone to landslides and soil erosion which then contributed to the main water pollution issues in the network of river system, sedimentation and siltation. The continuous trend of river water quality deterioration in Cameron Highlands has raised the issues for discussion in this review article. The purpose of this review is to briefly summarize the land use change, agriculture practices, agro-tourism, and agriculture policy and management toward water quality of the river system network in Cameron Highlands specifically in the downtown where most of the development and agriculture activities are concentrated. A rigorous review has been done on the existing literature to determine the relationship between land use change and agriculture practices toward river water quality in Cameron Highlands from 2001 to 2017. The total number of reviewed papers was 68. The outcomes established from previous researchers have highlighted factors such as soil erosion, landslides, agriculture activities, urbanization, and unplanned development associated with land use change have significantly influenced the river water quality in the highland areas. Continuous land use changes without proper development plan and law enforcement may critically threaten the sustainability of river network in the highlands area. Keywords: Agriculture, River water quality, Highlands, Land use, Soil erosion, Cameron Highlands Introduction provides water resources for agricultural, industrial, and Land use is the utilization of land resources by humans for domestic use downstream (Roozitalab et al. 2013). The various land activities and purposes such as for recreational areas that have elevation more than 1000 m are categorized (park), transport (road and railway), agriculture (farm), resi- as mountains, 100 to 1000 m as hills, and 30 to 100 m as dential (housing and settlements), and commercial (busi- developable land (Gasim et al. 2009). According to Malaysia ness and factories) (Rendana et al. 2015). Land use/land Islands and Highlands Development Guideline, any forest change (LULC) alter the natural ecosystem services via (1) lands situated 1000 m above the sea level are classified as modifying the ecological structure and functions, (2) influ- reserved forest or catchment forest land. Thus, any land encing human demand for ecosystem services, (3) affecting clearing is prohibited in this area as it is an environmentally the non-natural capital (e.g., infrastructure) providing hu- sensitive area (Tan and Mokhtar 2011). Moreover, high alti- man access to ecosystem services (Sonter et al. 2017). tude results in higher rate of chemical loss from soil erosion Highland regions act as water catchment and serve as the into the river (Saadati et al. 2012) and cultivation on steep main hydropower generation sources for lowland. It also slopes areas triggered soil erosion (Lantican et al. 2003). Common steps in opening new land for agriculture are land clearing, burning, land leveling, terracing, bed preparation, * Correspondence: [email protected] 1Department of Environmental and Occupational Health, Faculty of Medicine and planting (Aminuddin et al. 2001). Agriculture practices and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Selangor, done in fragile highlands area especially in steep slopes tend Malaysia Full list of author information is available at the end of the article © The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Razali et al. Ecological Processes (2018) 7:19 Page 2 of 17 to cause an on and off farms pollution toward the environ- which then fused with Tembeling River and form Pahang ment (Barrow et al. 2009). River (459 km), the longest river on Peninsular Malaysia and In Peninsular Malaysia, the main highlands regions in- drains into the South China Sea (Khalik et al. 2013a;RTD cluding Upper Perak-Galas, Upper Pergau, Upper Kinta- 2018a). On the westward, the rivers are being drained into Jelai, Upper Jelai-Tahan, Upper Selangor-Semantan, and the Perak River into the Straits of Melaka. This complex Upper Endau-Rompin (Rozimah and Khairulmaini 2016). river system consists of 123 tributaries particularly located Cameron Highlands is the smallest district of Pahang bor- within the Telom River and Bertam River. These rivers serve dering Kelantan on the north, Perak on the west, and Lipis as freshwater sources, hydroelectricity generation, and irriga- district on the south-east (Fig. 1). The total area of Cameron tion for agriculture purposes and are for recreational activ- Highlands is 71, 225 ha comprising of three main sub- ities (Gasim et al. 2009). Tourism and highland agriculture districts (mukim) which are Hulu Telom (63, 990 ha), Ring- are the main economies driven in Cameron Highlands. let (5, 165 ha), and Tanah Rata (2070 ha). Cameron High- In 2015, there was an almost 3% reduction on forest landsisoneofthemostfamous retreat locations in coverage in Cameron Highlands, and the land use for agri- Malaysia located in the high-elevation central of Titiwangsa culture activities has increased. Inefficient law enforcement Range, where the highest peak is Gunung Irau (2110 m). have cause many illegal land clearings, which trespass the Approximately, more than 74% of the total area has an forest reserve and riverbank areas, and unsustainable devel- elevation of more than 1000 m with a cold climate and oping methods (e.g., farming on steep slopes, rain shelter, scenic landscape. According to Cameron Highlands Local installation of irrigation pipes on the road sideways and in Development Plan (RTD 2018a), almost 29% of the land in the slope, excessive usage of pesticides and fertilizers, soil Cameron Highland are having steep slopes with a gradient erosion and high sedimentation rate in riverbed) have create greater than 25° (18,226 ha, 26%) to 35° (2039 ha, 3%). Areas major ecological disturbances in Cameron Highlands (Raj with steep slopes exceeding 25° have a high risk of soil 2002; Aminuddin et al. 2005;Barrowetal.2009; Khairul- erosion and are not suitable for development (Aminuddin et maini and Fauza 2010; Mohd Ariffin et al. 2014;Weebers al. 2001;RTD2018a). Located in a highland elevation, the and Idris 2016). average temperature of Cameron Highlands is between 17 ° National Audit Report 2012 in RTD 2030 has highlighted C and 20 °C all year round. However, the local temperature several issues of agriculture development of Cameron High- has risen up to 5 °C in 2014 compared to the past 15 years lands (RTD 2018b). Intensive land clearing and deforestation (RTD 2003). Maximum rainfall (wet season) is during Octo- for agricultural activities were reported in this area where ber to November and April to May while minimum rainfall most of the agricultural activities were operated illegally (dry season) is during January to March and June to August. without the permission of the authority. There also issues of There are three main rivers that flow across Cameron High- poor collaboration and coordination between authorized lands which are the Telom River (37 km) at the north, Ber- stakeholders (i.e., land and mines office) on the granting of tam River (20 km) at the middle, and Lemoi River (16 km) permits and approvals for land use even in the sensitive and (Fig. 2). All these rivers flow eastward to form the Jelai River high-risk areas, although the action does not comply with Fig. 1 Case study location located in Cameron Highlands, the smallest district in Pahang, Peninsular Malaysia (RTD 2018a) Razali et al. Ecological Processes (2018) 7:19 Page 3 of 17 Fig. 2 Map of Cameron Highlands with three major sub-districts: Hulu Telom, Tanah Rata and Ringlet. The map also visualizes the rivers channel networks within the highlands area (RTD 2018a) the conditions according to the environmental depart- agriculture practices, agro-tourism, and agriculture policy ment and the department of water and drainage. Further- and management toward the river system in highlands more, inadequate law enforcement action on trespassing area, Malaysia. The total numbers of paper reviewed were and illegal activities in this area had caused the agricul- 68. The literature search was performed through major tural activities to continue breaking the laws. This has scientific literature databases including Scopus, Science been proven by satellite images, where the land clearing Direct, Springer, Google Scholar, and EZproxy UPM for a new development of the agricultural area has library search engines with the following keywords: Cam- exceeded the permitted area by the authority.