Forest Cover and Change in Corozal District, Belize 2005 - 2011 - 2015
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FOREST COVER AND CHANGE IN COROZAL DISTRICT, BELIZE 2005 - 2011 - 2015 November 16, 2015 JAN MEERMAN, BELIZE TROPICAL FOREST STUDIES, P.O. BOX 208, BELMOPAN, BELIZE Neuland Rheinländer Mennoniten, S-E Corozal District. Prepared for: Corozal Sustainable Future Initiative, Mr. Heron Moreno P.O. Box 52, Corozal, Belize. Meerman. J.C., 2015. Corozal District Forest Cover Change 2005-2015 | P a g e 1 Abstract At the request of CSFI and ITCF, a forest cover change assessment was conducted utilizing a series of 30 m resolution Landsat TM satellite images following a supervised classification followed by a manual correction. Sufficiently cloud free images were available for 2005, but not for 2010. For this reason the analysis was carried out using cloud free 2011 image. Similarly, as it was not possible to locate cloud free images of the sample year 2015, a cloud free 2014 image served as baseline. For this project, forest is defined as closed canopy, mature natural broadleaf forest and took particular care not to classify secondary growth that was part of an agricultural cycle of slash and burn, as “forest”. The study found an average deforestation rate of approximately 0.6% for the 2005-2011 period, and an annual rate of 2.3% for the 2011-2015 period. The latter figure is indicates a significant acceleration of the deforestation rates in the Corozal district and is substantially higher that the rates identified in recent national studies which followed a comparable methodology. Introduction The Corozal Sustainable Future Initiative (CSFI) that with support from the International Tropical Conservation Foundation (ITCF) Manages the Shipstern Conservation and Management Area as well as the Honey Camp National Park and Freshwater Creek Forest Reserve is very concerned about the level of deforestation that is occurring around these protected areas. The Shipstern Conservation and Management Area is considered to be the Northern most node in the Northern Belize Biological Corridor, linked through a network of protected or otherwise forested areas. For Belize as a country, previous assessments of forest/vegetation/land use cover and change were carried out by a number of researchers starting in 1959 (Wright et al.,1959). As satellite images started to become available and with the development of remote sensing techniques, a large number of studies followed (White et al, 1996; Zisman et al, 1998; White et al, 2001; Meerman & Sabido, 2001; DiFiore, 2002; Ek, 2004; Penn et al, 2004; Emsch et al, 2000) These studies followed different methodologies and often focused on limited geographical regions or on specific floristic elements (e.g. Zisman et al, 1998 focusing on Mangroves; DiFiore, 2002 focusing on riparian forest of the Belize River). Belize Tropical Forest Studies, with the support of Conservation International (CI) and the Critical Ecosystem Partnership Fund (CEPF) conducted a study to map for Belize the change in forest cover between c.1990, c.2000 and c.2005. While Cherrington et al. (2010) calculated forest loss over the period 1980 – 2010. Methodology For this project, forest is defined as closed canopy, mature natural broadleaf forest. There exist many definitions as to what constitutes “forest”, but more and more, forest cover is being defined by what can be detected using remote sensing in combination with the methodologies used. For the Corozal district, 12 different ecosystems (Table 1., cf. Meerman & Sabido, 2001) are classified as “Forest” in this study. The most problematic in this definition is the “Deciduous Broad- leaved lowland shrubland, poorly drained”. This ecosystem is very widespread in Eastern Corozal and forms a transition from closed forest to herbaceous swamps and salt marshes. The forest Meerman. J.C., 2015. Corozal District Forest Cover Change 2005-2015 | P a g e 2 canopy of this ecosystem is quite variable and the distinction between these three ecosystems is often difficult to make on the basis of medium resolution remote sensing imagery. Problematic too, were areas with secondary growth. This is common around the villages and often difficult to interpret. Correct classification was often possible when comparing the area with satellite images of a number of years. These typically revealed the “shifting cultivation” nature of agriculture in these areas. Such secondary forests were not considered “Forest” as they can be presumed to be a component of an agricultural system. Forest cover and change was mapped by analyzing Landsat satellite imagery from 2005, 2011, 2014 and 2015 (table 2, Figures 1-4). The 2011 date was chosen because there was no cloud free image available for 2010. The Landsat 7 images were plagued by the SLC failure errors that occurred in 2003 resulting in no-data stripping, or gaps, these necessitating manual corrections. The 2014 Landsat 8 image did not have this problem, but no sufficiently cloud free Landsat 8 image was available for 2015. The spectral images delivered by the Landsat sensors cover all tropical land and clearly reveal forest versus non-forest land cover. The data resolution of 30 m is fine enough to detect clearings or patches of forest smaller than 1 hectare, but in most cases the minimum polygon size has been kept to 5 hectare. Software used included ERDAS Imagine 9.2 and ESRI ArcGIS 10.2.1. The overall methodology used for the classification is outlined in Steininger et al. 2006. The basis for the analysis was the 2014 Landsat 8 image which was virtually cloud free and free of SLC failure gaps. The 2015 Landsat 7 image was then used to manually add visible deforestation that had taken place between November 2014 and August 2015. To overcome the problem of identification of the “Deciduous Broad-leaved lowland shrubland, poorly drained” versus herbaceous swamps and salt marshes, the area was compared with high resolution images available as “basemap” in ArcGis 10.2.1. Table 1 Ecosystems in the Corozal District, defined as “Forest” UNESCO UNESCO description Code IA3a(1)(a) Tropical semi-deciduous broad-leaved well drained lowland forest IB1a(2) Tropical deciduous microphyllous lowland forest, well drained IA2a(1)(b)K Tropical evergreen seasonal broad-leaved lowland forest on calcareous soils IA2f(2)(a) Tropical evergreen seasonal broad-leaved alluvial forest, occasionally inundated IA2g(1)(a)-T Tropical evergreen seasonal broad-leaved lowland swamp forest, tall variant IA2g(1)(a)-Sh Tropical evergreen seasonal broad-leaved lowland swamp forest, short tree var IIIA1b(a) Deciduous broad-leaved lowland shrubland, poorly drained IA5a(1)(a) Caribbean mangrove forest; dwarf mangrove scrub IA5a(1)(c) Caribbean mangrove forest; mixed mangrove scrub IA5a(1)(d) Caribbean mangrove forest; coastal fringe mangrove IA5a(1)(e) Caribbean mangrove forest; riverine mangrove IA5a(1)(f) Caribbean mangrove forest; basin mangrove Meerman. J.C., 2015. Corozal District Forest Cover Change 2005-2015 | P a g e 3 Table 2. Landsat tm scenes utilized Path Row Date 2005 Date 2011 Date 2014 Date 2015 019 047 Landsat 7: 18/03/2005 Landsat 7: 04/04/2011 Landsat 8: 14/11/2014 Landsat 7: 15/08/15 Figure 1. Landsat tm 7of 18 March 2005. Note modest cloud cover and SLC failure gaps to the sides of the image. Meerman. J.C., 2015. Corozal District Forest Cover Change 2005-2015 | P a g e 4 Figure 2. Landsat tm 7of 4 April 2011. Note essentially cloud free cover and SLC failure gaps to the sides of the image Meerman. J.C., 2015. Corozal District Forest Cover Change 2005-2015 | P a g e 5 Figure 3. Landsat 8 image of 14 November 2014. Essentially cloud free. Meerman. J.C., 2015. Corozal District Forest Cover Change 2005-2015 | P a g e 6 Figure 4. Landsat TM 7 of 15 August 2015. Note extensive cloud cover and SLC failure gaps to the sides of the image. Meerman. J.C., 2015. Corozal District Forest Cover Change 2005-2015 | P a g e 7 Results Based on the maps and methodology used, the entire Corozal district measures 472,781 acres or 191,328 hectares. Meanwhile, forest cover in the Corozal district measured: 2005: 261,131 acres, 105,676 hectares 2011: 252,101 acres, 102,022 hectares 2015: 229,888 acres, 93,032 hectares Figure 5. Areas deforested between 2005, 2011 (orange) and 2015 (in red). Note that deforestation is particularly high in both northern Corozal and Eastern Corozal district. Meerman. J.C., 2015. Corozal District Forest Cover Change 2005-2015 | P a g e 8 Annual rate of deforestation The analysis focused on the loss of forest in hectares. However, deforestation is usually expressed in percentages. The annual rate of change is calculated by comparing the area under forest cover in the same region at two different times and expresses the difference as a percentage. Over time different formulas have been used to calculate the annual rate of change (see Puyravaud, 2003). The most influential is the formula prescribed by the FAO (1995), which states that the annual rate of forest change should be calculated using a formula that is derived from the Compound Interest Law. In an attempt to unify calculation methods and avoid confusion, Puyravaud (2003) devised a new formula which is used here: Where and is the forest cover at time respectively (the unit: per year or percentage per year). When this calculation is carried out, the following figures appear (table 3) Table 3. Annual Rate of deforestation in percentages 2005-2011: r = 0.17 ln 102,022/105,676 = 0.6% 2011-2015: r = 0.25 ln 93,032/102,022 = 2.3% Therefore the current study finds an annual deforestation rate for the Corozal district that has accelerated from of 0.6 % in the 2005-2011 period to 2.3% in the 2011-2015 period.