Greater loss and fragmentation of savannas than forests over the last three decades in Yunnan Province, China

Abstract

Yunnan Province, southwest China, has a monsoonal climate suitable for a mix of fire-driven savannas and fire-averse forests as alternate stable states, and has vast areas with savanna physiognomy. Presently, savannas are only formally recognised in the dry valleys of the region, and a no-fire policy has been enforced nationwide since the 1980s. Misidentification of savannas as forests may have contributed to their low protection level and fire-suppression may be contributing to vegetation change towards forest states through woody encroachment. Here, we present an analysis of vegetation and land-use change in Yunnan for years 1986, 1996, 2006, and 2016 by classifying Landsat imagery using a hybrid of unsupervised and supervised classification. We assessed how much savanna area had changed over the three decades (area loss, fragmentation), and of this how much was due to direct human intervention versus vegetation transition. We also assessed how climate (mean annual temperature, aridity), landscape accessibility (slope, distance to roads), and fire had altered transition rates. Our classification yielded accuracy values of 77.89%, 82.16%, 94.93%, and 86.84% for our four maps, respectively. In 1986, savannas had the greatest area of any vegetation type in Yunnan at 40.30%, whereas forest cover was 30.78%. Savanna coverage declined across the decades mainly due to a drop in open parkland savannas, while forest cover remained stable. Savannas experienced greater fragmentation than forests. Savannas suffered direct loss of coverage to human uses and to woody encroachment. Savannas in more humid environments switched to denser vegetation at a higher rate. Fire slowed the rate of conversion away from savanna states and promoted conversion towards them. We identified remaining savannas in Yunnan that can be considered when drafting future protected areas. Our results can inform more inclusive policy-making that considers Yunnan’s forests and savannas as distinct vegetation types with different management needs.

Tillage agriculture and afforestation threaten tropical savanna plant communities across a broad rainfall gradient in India

“…These findings confirm that old-growth savannas in India face similar consequences of land-use change as tropical and sub-tropical savannas in South America (Ferraro et al, 2021;Haddad et al, 2021;Koch et al, 2016), Australia (Fensham et al, 2016) and Africa . In doing so, this study offers evidence for why conservation efforts in India, as well as other parts of Asia, where savannas have been historically overlooked and undervalued, should seek to limit agricultural conversion and afforestation of old-growth savannas (Joshi et al, 2018;Lapuz et al, 2021;Ratnam et al, 2016).…”

“…While a multitude of drivers of global change are transforming Earth's grassy biomes, land‐use change has emerged as an acute and widespread cause of biodiversity loss in tropical savannas (Lapuz et al., 2021; Newbold et al., 2016; Parr et al., 2014). Much of our understanding on the ecological consequences of land‐use change for tropical savanna plant communities comes from studies in South America (e.g., Almeida et al., 2011; Cava et al., 2018; Laste et al., 2019) or has been inferred from studies of subtropical savannas in North America (Kirkman et al., 2004), southern Africa (Zaloumis & Bond, 2016) and Australia (Fensham et al., 2016).…”

A regional assessment of ecological environment quality in Thailand special economic zone: Spatial heterogeneous influences and future prediction

“…As a logistics and industrial hub, the EEC is promoted with extensive transportation projects, which imply severe impacts on ecosystems. Therefore, we also involved proximity to towns and transportation systems in the analysis to represent human accessibility and direct impacts on ecosystems and, to some extent, reflect the rapid development in this region compared to others Lapuz et al, 2021). We also endeavor to include socioeconomic factors in the analyzes to obtain a diversely T A B L E 1 Main LULC categories adopted from land use units of the LDD.…”