Ethiopian Orthdox church forests provide hydrological ecosystem services: evidence from stream sediment and aquatic insect analyses

Background/Question/Methods

Sacred natural sites represent unique micro-ecosystems whose local and regional ecosystem service delivery potential has only begun to be explored.  In northern Ethiopia there are over 7,800 Ethiopian Orthodox "church forests", small groves of native Afromontane forests surrounding church buildings, and in many cases these forests represent the only stands of native tree in the midst of vast degraded agricultural landscapes. Studies of church forests to date have explored major ecological determinants of forest composition (elevation, gradient, species availability) as well as key drivers of church forest degradation (primarily pressures from livestock and agricultural expansion, among other direct and indirect pressures on forests). But the potential hydrological services provided by church forests (in terms of water purification, flow regulation, and habitat for aquatic life) remain to be studied.  We tested the effect of church forest presence on water sediment loads and macroinvertebrate abundance and biodiversity in six streams flowing from open agricultural land through or alongside church forest groves in Amhara, Ethiopia. We collected 56 water and aquatic insect samples from sites upstream of church forests, within or alongside church forests, and downstream of church forests, and compared sediment content (inorganic and organic) and macroinvertebrate community indices to assess the potential contributions of church forests to downstream water quality.

Results/Conclusions

Total suspended solids (TSS) upstream of church forests averaged 0.29 g l^-1 , but upon entering a church forest with extensive indigneous vegetation average TSS dropped to 0.19 g l^-1. However the effect was relatively short-lived: upon leaving the church forest, streams quickly responded to surrounding land uses and returned to relatively high TSS levels within 250m after flowing back into degraded agricultural land. Nevertheless, streams do appear to respond - even at a small spatial scale - to the protection afforded by natural forest cover in Ethiopian church forests. Indeed, preliminary analyses of macroinvertebrates in these same streams revealed high diversity, including presence of sensitive taxa, in streams passing within the church forest sites, while stress-tolerant species including Gastropoda and Chironomids dominated both upstream and downstream sampling sites. The findings of this research showcase the potential for church forest ecosystems to contribute to stream health, suggesting these small forest patches might be incorporated into broader regional watershed conservation strategies in northern Ethiopia.