Browsing by Author "Zahawi, Rakan A."

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    Effects of landscape structure on restoration success in tropical premontane forest
    San-Jose, Miriam; Werden, Leland K.; Joyce, Francis H.; Reid, J. Leighton; Holl, Karen D.; Zahawi, Rakan A. (Nature Portfolio, 2022-08-04)
    Reversing large-scale habitat degradation and deforestation goes beyond what can be achieved by site-level ecological restoration and a landscape ecology perspective is fundamental. Here we assess the relative importance of tree cover and its configuration on forest-dependent birds and late-successional tree seedlings in restoration sites in southern Costa Rica. The abundance and species richness of birds increased in landscapes with more corridors, higher tree cover, and lower levels of fragmentation, highlighting the importance of riparian corridors for connectivity, and continuous tree cover as suitable habitat. Landscape variables affected abundance and species richness of seedlings similarly, but effects were weaker, possibly because seedlings face establishment limitation in addition to dispersal limitation. Moreover, the scale of landscape effects on seedlings was small, likely because proximal individual trees can significantly influence recruitment in restoration plots. Results underscore the importance of incorporating landscape-level metrics to restoration projects, as knowing the extent, and how the landscape may affect restoration outcomes can help to infer what kind of species will arrive to restoration plots.
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    How feasible are global forest restoration commitments?
    Fagan, Matthew E.; Reid, J. Leighton; Holland, Margaret B.; Drew, Justin G.; Zahawi, Rakan A. (2020-01-16)
    Numerous countries have made voluntary commitments to conduct forest landscape restoration over millions of hectares of degraded land in the coming decade. We consider the relative likelihood these countries will achieve their restoration commitments. Across countries, the area committed to restoration increased with existing forest and plantation area, but was inversely related to development status, with less developed countries pledging more area. Restoration commitments are generally large (median: 2 million hectares) and will be challenging to meet without the wholesale transformation of food production systems. Indeed, one third of countries committed >10% of their land area to restoration (maximum: 81%). Furthermore, high rates of land cover change may reverse gains: a quarter of countries experienced recent deforestation and agricultural expansion that exceeded their restoration commitment area. The limited progress reported by countries, and the sheer scale of commitments, raises serious questions about long-term success, especially absent necessary monitoring and management plans.
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    Multi-scale habitat selection of key frugivores predicts large-seeded tree recruitment in tropical forest restoration
    Reid, J. Leighton; Zahawi, Rakan A.; Zarrate-Chary, Diego A.; Rosales, Juan A.; Holl, Karen D.; Kormann, Urs (Wiley, 2021-12-01)
    Large-seeded, animal-dispersed (LSAD) trees include some of the most valuable and threatened species in the tropics, but they are chronically underrepresented in regenerating forests. Toucans disperse many LSAD species, so attracting toucans to regenerating forests should help re-establish more diverse tree communities. We ask: (1) What constitutes suitable toucan habitat in premontane southern Costa Rica? (2) How much do small-scale restoration strategies influence toucan visitation compared to landscape-scale habitat suitability outside of restoration sites? (3) How well does toucan visitation predict the richness of LSAD tree species recruiting into regenerating forests? We combined habitat suitability models with long-term toucan observations and comprehensive tree recruitment surveys to assess these questions in a multi-site forest restoration experiment. Restoration treatments included tree plantations, natural regeneration, and applied nucleation. Habitat suitability obtained by modeling for three sympatric toucan species was predicted by elevation and the extent and age of landscape forest cover. Within suitable landscapes, toucans visited areas restored via tree planting ≥5 yr sooner and ≥2× more often than plots restored via natural regeneration. Tree plantations in suitable toucan habitat at the landscape scale had LSAD tree recruitment communities that were 2–3× richer in species than plantations in poor toucan habitat, and 71% (15/21) of all recruiting LSAD tree species were found only in plantations where landscape habitat was suitable for the largest toucan, Ramphastos ambiguus. Results support a multi-spatial-scale model for predicting toucan-mediated dispersal of LSAD trees. Tree planting increases toucan visitation and LSAD tree recruitment, but only within landscapes that represent suitable toucan habitat. More broadly, habitat suitability modeling for key seed dispersers can help prioritize restoration actions within heterogenous landscapes.