Area Exclosure as a Strategy for Climate Change Mitigation: Case Study from Tigray Region, Northern Ethiopia

Abstract

Forests provide multiple benefits for communities. One of these is global climate change combating with carbon sequestration. Exclosures are a particularly important class of restoration and vegetation generating these benefits. Institutional arrangements to govern these commons are believed to substantially influence carbon storage and livelihood contributions, especially when they incorporate local knowledge and participatory decision-making. However, hypothesized relationships between institutional factors and benefits have never been tested on data from exclosures found in Tigray. A total of 120 quadrants were sampled using a stratified preferential sampling design technique with flexible systematic model and 180 household respondents were surveyed with multistage stratified random sampling procedure. The differences in carbon stocks and vegetation composition between an exclosure age and free grazing land were assessed using a paired t-test. All exclosures displayed higher ECS (ecosystem carbon stock), and plant species richness, diversity, and aboveground standing biomass than the free grazing lands. Differences in ECS between exclosures and free grazing lands varied between 32.96 and 61.0 t ha 1 and increased with exclosure age. Over a period of 20 years, the carbon dioxide sequestered in the investigated exclosures was 223.88 t ha 1, total soil nitrogen increased by 2.93 t ha 1 and additionally available phosphorus stocks amounted to 40 Kg ha 1. Carbon is especially sensitive to population pressure, with an increase in population per hectare of 100 people associated with reduced carbon of 96% and 89% carbon per hectare and carbon per household, respectively. More remote areas also tend to have more carbon, with an increase in distance to the town of 1 kilometer associated with a 6–7% increase in carbon. Similarly, the findings on the social and cultural influences will affect exclosure management for other ecological values, such as habitat conservation and water quality, as well as their likelihood to respond to policies that promote these values. Thus, the findings are relevant for a broader range of natural resource issues than restricting only on carbon- and climate change-related issues.