The Impact of Forest Degradation on Carbon Stocks of Forests in the Matiwane Area of the Transkei, South Africa
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The impact of forest degradation on carbon stocks of forests in the Matiwane area of the Transkei, South Africa A thesis submitted in fulfillment of the requirements for the degree MASTER OF SCIENCE At RHODES UNIVERSITY By KAGISO MANGWALE 2010 Abstract This study focused on assessing the condition and creating a carbon inventory of forests in the Matiwane area of the Transkei. This entailed the use of aerial photography in tracing forest cover change from 1942 to 2007 coupled with ground-truthing to assess whether the forests have in any way endured degradation over the years with a potential reduction in carbon stocks as a result. This study revealed both the loss and gain of biomass in the area with a general trenrl of forests bei11g continuously converteJ io agricultural fields resulting in reduced forest area, stem density, tree density and carbon loss in different pools of the forests, reflecting that these forests are degraded. The conversion has resulted in the reduction in the number of species from a mean of 11±0.57 species/200m2 in intact forests to 1±0.23species/200m2 plot in degraded forests. It was also revealed that approximately 5.2 % (791 hectares) of 15 352 hectares of forest area was lost as a result of the conversion of forest land to agricultural fields from 1942 to 2007 with 99 % of the clearing occurring in the last 33 years (1974-2007) and of which 60 % ( 4 77 hectares) occurred from 1995 to 2007, indicating that forest degradation in these forests is on the increase. The assessment also revealed some areas that were non forest in 1942 that have accumulated woody biomass (BAA), composed mainly of Acacia sp accounting for 51.18 MgC.ha-1 (Megagrams of carbon per hectare) and total carbon stocks of 0.02 TgC (Teragrams of carbon). The degradation of these forests induced a reduction in carbon stocks from 311.68±23.69 MgC.ha-1 (to a soil depth 0-50 em) in intact forest to 73.46±12.34 MgC.ha-1 in degraded forests. The total carbon stocks in the degraded forests were approximated at 0.06 TgC and the BAA areas 0.02 TgC with 4.7 TgC in intact forests. The degradation of these forests has resulted in the net carbon loss of 0.19 TgC between 1942 and 2007 but 4.76 TgC is still locked in these forests. The large difference in carbon stocks between intact and degraded forests indicated the need to reduce the degradation of these forests to prevent further carbon loss and reduction of the carbon sequestration potential of these forests. ii Acknowledgements I would like to extend my gratitude to the following people: My supervisors Professor Charlie Shackleton & Dr Ayanda Sigwela, who gave direction to this research, provided the necessary inputs, support and guidance throughout this research. It was not easy but through your motivations the work came to a successful completion. Mike Powell, who provided the guidance on methodological matters during this research. Mike you went out of your way to help out and I couldn't have managed without your help. The Department of Water Affairs through the Working for Woodlands program, for the funding. I would like to thank again the forest managers Mr Mgqudlwa and Mr Mkibi for all their help. Rirhandzu Mkhari & Malibongwe Makafe who went out of their way to help with data collection and field work. You guys sacrificed your bodies and time, to help out in this research. Makafe, I am indebted to you my bra, you were the cornerstone of this research, ndiyabulela mhlobo warn. The family at the Environmental Science department, for all their help. To my friends, thank you guys for the support and the crazy moments that kept me going during this last two years. The people at S22 chemistry department, I became part of your family and thanks a lot. Nicole Sibuyi, you made this happen, thank you. To my family, Ke Lebogile. Mma Rebecca, mma Lucy, mma Sarah le Nape-tsohle ke ka lebaka la lena BAKGADITSI, DI TAU. KE BUSETSA DITEBOGO GO LENA KA MOKA. Ke fihlise ditebogo gape go Maureen, Florence, Mary le lelapa ka moka- ka thekgo le !erato la lena ke kgonne, ka tielela go fthla ga bjale. Ke a le rata ka moka. iii Make your own notes. NEVER underline or write in a book. Table of contents Abstract. ............................................................ ............................................................. .ii Acknowledgements ................ ............................................... .. ...................................... iii Table of contents ......... ..... ......... .. .. .. ........ ....................... ......................... ....................... iv List oftables .. ........... .. ................................................................................................... vii List of figures ................. .............................. ................................................................ viii List ofabbreviations ............................................................ ........................................... ix CHAPTER 1 ................. ...... ................................................ .................. ..................... ..... 1 1. Introduction ................. ... ......... ............... .................................................................. 2 1. 1 Overview .. ........................................... ..... .. ......................................................... .. 2 1.2 Motivation for the research ................................................................... .. .......... ..... 3 1.3 Objective and Research questions ..................................... ..................................... 3 1.4 Literature review .. ............. ............................................... .. ........................ ............ 4 1.4.1 Global warming and forests ............................................................................. 4 1.4.2 Carbon sequestration by forests ....................................................................... 5 1.4.3 Forest degradation and deforestation .. .......................................... ....... ............. 6 1.4.4 Forest restoration and the carbon market ................ ..................................... ........ 9 1.4.5 The need for South Africa to engage in carbon studies in forests .................... 10 1.4.6 The need for the assessment ofthe condition and carbon stocks of South African forests ............... .................................. .. ........................... .......................... 16 1.4.8 Degradation and deforestation of South African forests ................................. 19 1.4.9 Transkei forests ................................ .. ................ ........................................... 21 1.5 The coastal forests of the Matiwane ................. ........... ............... ........ .. .. .............. 23 1.5.1 Administrative structures ............................................................................... 23 1.5.2 Climate and Geology ............ ................................................... .. .................... 25 1.5.3 Forests in the area and forest degradation........ ......................... ...................... 26 1.5.4 Conservation activities ... ........... .. ........... .. .. ................................................. .. 27 CHAPTER 2 ....................................................................................... ............................ 2 2.1 Introduction ............................ ........................................................ ......................... 30 iv 2.2 Materials and Methods ............................................................................................ 32 2.2.1 Assessing forest cover change ............ .................. .. ........................................... 32 2.2.2 Assessing the cause and the impact offorest cover change ................. ............... 32 2.2.3 Data analysis ...... ............................................................................................... 33 2.3 Results ....................................... .............................................................................. 33 2.3.1 Forest cover change .. ......................................................................................... 33 2.3.2 The main cause of forest degradation ................................................................ 35 2.3.3 Biomass accumulated areas (BAA) ................................................................ ... 36 2.3.4 Forest composition ofthe two forest states and BAA patches ............................ 37 2.3.5 Comparing the intact forests in reserves with the ones off the reserve ....... ...... 38 2.4. Discussion .............................................................................................................. 39 2.5. Conclusion ....................................... .............................. ... ..................................... 44 CHAPTER 3 ........................................ ......................................................................... 30 3 .1. Introduction ................................................... ......................................................... 46 3.2 Materials and methods ..................................................................................... ... 48 3 .2.1 Developing the hardwood and softwood allometric equation ... .................... .48 3.2.2 Selecting the best form of the equation ....................................................... .48 3 .2.3 Comparing the Matiwane hardwood