The Impacts of Landscape Fragmentation and Climate Change on Ecosystem Service Provision in Nigeria

Abstract

Ecosystem services (ES) are vital to human survival and wellbeing – providing supporting, regulating, provisioning and socio-cultural benefits. ES delivery has been significantly impacted by human modification of natural ecosystems, affecting the costs and benefits people receive from ecosystems. These changes are driven by many anthropogenic drivers, including climate change, land cover change, pollution, and overexploitation of resources. In this thesis, I focus on landscape fragmentation and climate change, using Nigeria (Africa's most populous country) as a case study. My thesis aims: i) to quantify fragmentation of multiple land covers at the national and state levels to understand better the changes that occurred between 1992 and 2019; ii) to understand the influence of fragmentation of natural ecosystems and climate change on ES, focussing on crop yield and water availability (both provisioning ES), carbon storage (regulating ES) and recreation (cultural ES); and iii) to use future land cover and precipitation scenarios to estimate the potential future provision of ES, focusing on carbon storage (a regulating ES) and crop yield (a provisioning ES).

In Chapter 2, I use various fragmentation metrics such as the nearest neighbour distance (ENN_MN), the mean patch area (AREA_MN), the core area index (CAI_MN) the perimeter (square) of the patch (SHAPE_MN) to analyse patterns of land cover change, from 1992 through to 2019. I quantify the extent of landscape fragmentation in Nigeria at the state level. My results showed significant changes in land cover over the 27 years, with national-level increases in cropland 37.2% to 39.0%, with an overall increase of 14,470 km² (0.16% annual growth). Forest/woodland also grew significantly, increasing from 17.7% to 20.6%, representing a 25,224 km² gain (0.57% annual growth). In contrast, shrubland experienced a marked decline, decreasing from 13.8% to 8.4%), a loss of 51,586 km² (-1.50% annual decline). Grassland showed minimal change, with a slight decrease of 463 km² (-0.02% annual decline), and the 'other' category increased by 7,706 km² (0.15% annual growth). The fragmentation metrics revealed distinct spatial patterns. Cropland's mean patch area (AREA_MN) generally increased post-2000, while grassland and shrubland fluctuated, with shrubland experiencing mid-1990s peaks before declining. Forest/woodland exhibited significant declines in AREA_MN and mean patch core-area index (CAI_MN), particularly in Cross River, Kogi, and Oyo. Mean Euclidean nearest-neighbour (ENN_MN) values highlighted increased forest connectivity post-1998 but variable trends in other LULC categories. Cropland's mean shape index (SHAPE_MN) rose, reflecting more irregular patch shapes, while grassland and shrubland showed stabilisation after initial fluctuations. However, geopolitical zones within Nigeria exhibited varying patterns of change. For example, I find within-country differences in forest area change, likely linked to different drivers of deforestation, and varying policies and practices such as Land Use Act of 1978, National Policy on the Environment (Revised 2016), National Forestry Policy, National Action Programme to Combat Desertification (NAP), Great Green Wall Initiative, National Biodiversity Strategy and Action Plan (NBSAP), National Agricultural Resilience Framework (NARF)to prevent it. Deforestation in Lagos and Ogun is likely driven by population growth and industrial development, whereas in Rivers and Borno, cropland expansion and firewood/timber production are the likely drivers. This underscores the impact of human activities, such as population growth, urbanisation, and agricultural expansion on landscape structure.

In Chapter 3, I investigate the relationships between landscape fragmentation, climate change (precipitation), and the provision of ES - namely, crop yield, water availability, carbon storage, and recreation, at the state level. My results show that the provision of ES is affected by fragmentation and precipitation. Carbon storage correlates with precipitation levels alone, while precipitation levels and fragmentation metrics influence water availability and some crop yields. Notably, other crop yields and recreation services were solely influenced by fragmentation. I suggest possible processes that might drive these patterns. Overall, this chapter highlights the knock-on effects that changes in land cover and climate may have on ES.

In Chapter 4, I forecast the potential future supply of ES in Nigeria in 2050 by combining existing climate projections with expert-based estimates of future land cover change by 2050 to create novel spatial scenarios. The results showed that RCP8.5 scenario precipitation and RCP2.6 scenario precipitation for Nigeria have an uneven distribution of precipitation changes, with increased precipitation predominantly in northern states and southern states showing a decrease in precipitation, although northern states remain drier than their southern counterparts. My expert-based 2050 land cover change scenarios show modest land cover changes on a national scale, posing significant challenges to food security and well-being. However, when combined, my projections indicate declines in half of the investigated ES by 2050, including carbon storage and several essential crop yields, while showing stability or increases in others like palm oil and yam yields. The findings and insights from this chapter could contribute to developing effective strategies such as implementing Nature-Based Solutions (NBS), enhancing habitat connectivity, implementing adaptive management Practices, promoting sustainable land-use planning, and engaging local communities and indigenous knowledge to address the potential impact of fragmentation and climate change on ES.

This work in this thesis underscores the pressing need for strategic planning and integrated policy development to mitigate the unfavourable impacts of landscape fragmentation and climate change on Nigeria's ES. My findings aim to support Nigeria's efforts toward achieving the Sustainable Development Goals (SDGs) and enhancing human well-being by identifying areas of severe impact and highlighting successful mitigation strategies. The insights gained herein are critical for researchers, planners, land management experts, and decision-makers, fostering discussions that could lead to sustainable land resource policies and practices in Nigeria and similar contexts globally such as Sustainable Development Goals (SDGs), United Nations Convention to Combat Desertification (UNCCD), Paris Agreement on Climate Change, Forest Carbon Partnership Facility (FCPF), Global Soil Partnership (GSP) and Africa Union’s Agenda 2063).

Date of Award	28 Jan 2025
Original language	English
Awarding Institution	Bangor University
Supervisor	Simon Willcock (Supervisor) & Eleanor Warren-Thomas (Supervisor)