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Tropical landscapes are dominated by land‐use systems, but their contribution to the conservation of biodiversity is largely unknown. Since changes in biodiversity in response to human impact are known to differ widely among taxonomic groups and guilds, there is a need for multidisciplinary collaboration of plant, vertebrate, and invertebrate experts. We used inventories of trees, understory plants, birds (subdivided into endemics, insectivores, frugivores/nectar feeders), butterflies (endemics, fruit feeders), and dung beetles in Sulawesi (Indonesia) to characterize a gradient from near‐primary to secondary forests, agroforestry systems, and annual crops. As expected, overall species richness tended to decrease within this gradient of increasing habitat modification, but, in contrast to previous studies, we found the species richness between most taxonomic groups to be significantly correlated (36 out of 38 pairwise comparisons). However, on average only 48% of the variance could be explained (within the five main groups), and only a few taxonomic groups/guilds turned out to be good predictors for others: for example, trees for fruit‐ and nectar‐feeding birds (88% explanation) and fruit‐feeding butterflies (83%), endemic birds for endemic butterflies (72%), and frugivorous/nectar‐feeding birds for fruit‐feeding butterflies (67%). Although biodiversity of land‐use systems showed taxonomic group‐ and guild‐specific differences, most groups were affected in a similar way by habitat modification. Near‐primary forest sites proved to be of principal importance for conservation; however, land‐use systems such as secondary forests (for understory plants, birds, and butterflies) and agroforestry systems (for butterflies) supported relatively high numbers of species and might play a significant role for biodiversity conservation in tropical landscapes.

Although the Guinea-Congolian rain forest region is an important focal point for conservation in Africa, very little information is available on the effects of forest modification and land use on the region's biodiversity. We studied bird communities and vegetation characteristics in 24 sampling stations distributed over two near-natural forests (near-primary forest, secondary forest), and two land use types (agroforestry, annual cultures) in the lowlands of the Korup region, Cameroon. Repeated sampling was used to establish near-complete inventories of bird assemblages for each site. Despite a 90% average drop in tree basal area from forest to farmland, overall bird species richness did not decrease significantly with increasing habitat modification. However, different groups of birds responded in different ways. Frugivorous and omnivorous bird species richness did not differ between habitats, whereas richness in granivorous, flower-visiting, and nonbreeding species was higher in land use systems compared to forests. In contrast, insectivorous birds, especially terrestrial and large arboreal foliage gleaning insectivores, and ant followers showed a declining species richness from forest to farmland. Also, richness in species of those restricted to the Guinea-Congolian forest biome and of the family Pycnonotidae showed a pronounced decline with increasing habitat modification. Species richness of overall insectivores, terrestrial insectivores, large-and medium-sized arboreal foliage gleaners, ant followers, as well as pycnonotids and biome-restricted species, were strongly or even very strongly positively correlated with overstory tree density and, in most cases, also with basal area. In contrast, tree density and basal area were strongly negatively correlated with species richness of nonbreeding visitors and flower-visiting bird species. Species composition was most distinct between near-primary forest and annual culture sites, and the abundance of 23 out of 165 species was affected by habitat, suggesting considerable partitioning of habitat niches along the habitat gradient. Our results stress the importance of tree cover in tropical land use systems for the maintenance of resident forest bird populations and confirm that natural forest management is more beneficial for global bird conservation compared to other forms of forest exploitation, including agroforestry systems.

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There is still much debate over the potential value of land-use systems for the maintenance of tropical biodiversity. An increasing number of studies indicate that much forest biodiversity can also be found in the agricultural landscape matrix. Because there is little information on the potential value of land-use systems for tropical forest bird species, we conducted repeated point counts in near-primary forest, adjacent young secondary forest, modernized cacao agroforestry systems, and annual cultures at submontane elevations in central Sulawesi, Indonesia. Species richness decreased from natural forest and young secondary forest to agroforestry systems and annual cultures. Although species richness was similar between natural and young secondary forest, the number of endemic bird species was significantly lower in second-growth forest. Species composition gradually changed as the habitat changed from natural to secondary forest, agroforestry systems, and annual cultures. Despite close proximity to near-primary forest, the agroforestry systems studied supported only a few small frugivorous-nectarivorous species. Our results suggest that secondary forest could play an important role in the conservation of many Sulawesi bird species, but, although suitable for colonization, its potential to sustain populations over the long term is unknown. Improvement of the landscape matrix for biodiversity conservation through secondary habitats therefore seems desirable to enlarge the ranges of forest species, but the fight against land conversion within protected areas of the region should be of much higher importance, at least at present.Resumen: Aun hay debate sobre el valor potencial de los sistemas de uso de suelo para el mantenimiento de la biodiversidad tropical. Un creciente número de estudios indica que mucha de la biodiversidad del bosque también se encuentra en la matriz agropecuaria del paisaje. Debido a que hay poca información sobre el valor potencial de los sistemas de uso de suelo para especies de aves de bosque tropical, realizamos conteos por puntos repetidos en bosque casi primario, bosque secundario joven adyacente, sistemas agroforestales modernizados de cacao y cultivos anuales en elevaciones sub-montanas en Sulawesi central, Indonesia. La riqueza de especies decreció del bosque natural y bosque secundario joven a los sistemas agroforestales y cultivos anuales. No obstante la cercanía de bosque casi primario, los sistemas agroforestales estudiados soportaron solo a unas cuantas especies frugívoro-nectarívoras. Nuestros resultados sugieren que el bosque secundario podría jugar un papel importante en la conservación de muchas especies de aves de Sulawesi pero, aunque adecuado para colonización, se desconoce su potencial para sostener poblaciones a largo plazo. Por tanto, parece deseable un mejoramiento de la matriz del paisaje para la conservación de biodiversidad mediante hábitats secundarios para ampliar los rangos de las especies forestales, pero la lucha contra la conversión de suelos dentro deáreas pr...