Borneo whistler (Pachycephala hypoxantha), Bornean peacock-pheasant (Polyplectron schleiermacheri), Bornean blue-flycatcher (Cyornis superbus) and Bornean bristlehead (Pityriasis gymnocephala). A research cluster (): "Upsetting the balance in the Mahakam Delta: past, present and future impacts of sea level rise, climate change, upstream controls and human intervention on sediment and mangrove dynamics" extensively carry out research on the Mahakam. The cluster's objective is to study the impact of external forcing factors such as sea-level rise, climate change, upstream sediment, as well as human interference on past, present and future development of the Mahakam delta in different time scales. Pollution Logging and mining activities have contributed to the "alarming rate" of pollution of East Kalimantan's Mahakam River. Tests of water pollutants showed levels increased sharply between 2009 and 2011. Despite the growing pollution, it is claimed that "the water is basically still safe for consumption." Unsafe concentrations of heavy metals have been observed in Mahakam fish. A 2015 study found lead concentrations in excess of 1000 times safe levels along with unsafe levels of copper, zinc, and cadmium. Bridges Bridges include the Mahakam Bridge and the Kutai Kartanegara Bridge. The latter collapsed on 26 November 2011, it took 3 years of planning and one and half years more to rebuild new bridge on the same spot. The new Kutai Kertanegara Bridge has been open for public use since 8 December 2015, after an opening ceremony held by a local regent. Social aspect The River Mahakam is an economic resource for fishermen and farmers, and as freshwater source, as a waterway since ancient time until today. It is in this river basin where the Kutai kingdom evolved. The Kutai history is divided into two periods, Kutai Martadipura (around 350–400 AD) and Kutai Kartanegara period (around 1300). Kutai Martadipura, a Hindu kingdom founded by Mulawarman at Muara Kaman, is regarded as the oldest kingdom in Indonesia. Kutai Kartanegara was founded by settlers from Java at Kutai Lama near the mouth of Mahakam. In around 1565, Islam was extensively spread in Kartanegara by two Moslem preachers from Java, Tunggang Parangan and Ri Bandang. The Dayaks are the indigenous people inhabiting Kalimantan beside the Kutais and the Banjars. Since the 1970s transmigration of people to East Kalimantan was organized by the Indonesian government especially in areas near River Mahakam. Transmigration aims to migrate people from overpopulated Java, Bali, and Madura islands to stimulate greater agricultural productivity in outer