Estimation of the red deer population and its impact on the Tugay forest ecosystem in the Lower Amu Darya State Biosphere Reserve, Uzbekistan

Abstract

In 2011, the Government of Uzbekistan established the Lower Amu Darya State Biosphere Reserve (LABR). This reserve aims to conserve the Tugay, an endangered riparian forest ecosystem straddling the main rivers of Central Asia’s drylands, which is under extreme anthropogenic pressure. The LABR has reintroduced Bukhara red deer (Cervus hanglu bactrianus), a subspecies endemic to Asia whose numbers declined severely over the 20th century. The LABR development project aims to provide operational support to the Uzbek authorities for their application to join the World Network of Biosphere Reserves. GIZ (German Society for International Cooperation) requested CIRAD to provide a science-based estimate of the deer population in the LABR, using an internationally recognized method, and to issue recommendations to ensure ecologically and socio-economically sustainable management. The survey of the Bukhara red deer population began in October 2019. The study area covered 88 km2. The survey design consisted of 12 parallel straight lines 1400 m apart; the total transect length was 65 km. During the count, 127 observations of individuals or herds were made and a total of 336 individuals were observed. The data were analysed using DISTANCE 7.3 software. The encounter rates were 1.95 obs./km and 5.17 animals/km. The estimated density was 24 deer/km2 and the estimated total population was 2,112 deer [1,320 - 3,344, 95% CI]. The proportion of dead, dying or severely affected trees was roughly estimated at 10%, and the proportion of trees affected but with a good chance of survival at 15%. In the southern core area of the LABR, a very high proportion of seedlings and suckers was being eaten and the forest is no longer regenerating. Maintaining a population of 24 deer/km2 in the southern core area of LABR clearly seems incompatible with either the conservation of the Tugay forest ecosystem or the peaceful coexistence of deer with human populations adjacent to the LABR. Options to mitigate deer pressure include translocation to the northern core area of the LABR or other areas, and regulation of the deer population. The density is too high to ensure effective preservation of the species locally, although the deer population is under severe pressure in Asia as a whole.