156 S. C. Rafanoharana et al.


TABLE 1 The protected area categories system advocated by IUCN since 1994 (Phillips, 2004).


Category Function (official name) I


II


III IV V


VI


Strict protection (a, Strict nature reserve; b, Wilderness area


Ecosystem conservation & protection (National park)


Conservation of natural features (Natural monument or feature)


Conservation through active management (Habitat/ species management area)


Landscape/seascape conservation & recreation (Protected landscape or seascape)


Sustainable use (Protected areas with sustainable use of natural resources)


Estrada et al., 2017). Although assessing the current status of species is difficult, projecting the fate of species into the fu- ture adds another level of uncertainty. For lemurs this pro- jection has been attempted in the context of overall deforestation, fragmentation and climate change (Brown & Yoder, 2015; Morelli et al., 2020; Vieilledent et al., 2021; Steffens et al., 2022). Here we use an analysis of the extent of forest areas and


deforestation rates of all protected areas of Madagascar dur- ing 2015–2017 as a proxy for a formal assessment of lemur populations and to project their development within pro- tected areas for 2017–2050. Specifically, we seek to answer the following questions: (1) How did forest cover change in the protected areas of Madagascar during 2015–2017? (2) Did the forest cover change differently in protected areas of different IUCN categories? (3) Was the change in forest cover related to the size of the forest? From the an- swers to these three questions we project the size of forest blocks for 2017–2050, assuming that the current deforesta- tion rate of each protected area will remain constant. (4) Taking the size of forest blocks as a proxy for the relative number of individuals per forest block, we ask: how do con- servation assessments based on the reduction of the size of subpopulations change when based on projections of the total size of protected areas in 2050 and of the forest areas when considering distinct forest blocks within protected areas?


Methods


Estimating forest cover The approach used to assess forest cover has been described previously (Rafanoharana et al., 2021) and is summarized here only briefly. Within a larger project to estimate forest change for all of the protected areas of Madagascar, we an- alysed 114 terrestrial protected areas, considering humid


forest, dry western forest and south-western dry and spiny forests and thickets. We obtained the raw shapefile data from the protected area management system of the Ministry of Environment and Sustainable Development of Madagascar based on the legal document of creation. From our long-term historical dataset covering 1990– 2017 we used time series forest cover data for the years 2015 and 2017 (based on those from Vieilledent et al., 2018), which were the result of a combination of the 2000 forest cover map and annual tree cover loss maps at 30-m spatial resolution. We restricted the analyses to these 2 years because most of the new protected areas of IUCN categories IV and V were formally established only in 2015. The forest data used here have some biases because the remote sensing tools currently applied tend to underestimate forest cover in dry forest and overest- imate it in humid forest (Rafanoharana et al., 2023). Therefore, the data for the dry forests used here should be regarded as minimum values, and forest cover changes are likely to be higher. Almost 20% of the protected areas (22/111) comprise sev-


eral forest blocks; a block is defined as any non-contiguous shape within a protected area. These blocks are separated by a non-forest matrix, and thus the forested part of a pro- tected area is smaller than the total surface of the area. We did not consider the protected areas of Bemaraha,


Beza-Mahafaly and Zahamena because the delimitation of blocks was unclear at the time of analysis. These sites exper- ienced little deforestation during 2015–2017 (Bemaraha: 95,909 to 95,534 ha; Beza-Mahafaly: 521.26 to 521.16 ha; Zahamena: 69,008 to 68,792 ha). Their exclusion does not change the general conclusions of the analyses. Areas (either the protected area as a whole or the exact


size of the different non-contiguous forest blocks within any given protected area) were assigned to size classes of 0–9.99 km2, 10–19.99 km2, 20–39.99 km2, 40–79.99 km2, etc., doubling from one class to the next to $ 2,559 km2 (Fig. 1). We assume that all forest areas provide suitable habitat for all lemurs occurring in the region. This is improbable, and so this approach overestimates the area inhabited by lemurs.


Projecting forest loss during 2017–2050


Forest loss until 2050was estimated using the per cent of an- nual forest loss during 2015–2017 for each protected area separately. To check whether this period is representative of long-term deforestation rates we compared the annual rate during 2015–2017 with the deforestation rates over 5-year intervals during the previous 25 years. We included only the IUCN category I–III areas. We did not consider protected areas that changed in size during 1990–2015. The median annual deforestation rate for the remaining 45 areas (all of IUCN categories I–III) was 0.06% during


Oryx, 2024, 58(2), 155–163 © The Author(s), 2023. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605323001175


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