Jean-Michel Onana

Important Plant Areas: revised selection criteria for a global approach to plant conservation

Despite the severe threats to plant habitats and high levels of extinction risk for plant species in many parts of the world, plant conservation priorities are often poorly represented in national and global frameworks because of a lack of data in an accessible and consistent format to inform conservation decision making. The Important Plant Areas (IPAs) criteria system offers a pragmatic yet scientifically rigorous means of delivering these datasets, enabling informed national- or regional-scale conservation prioritisation, and contributing significantly towards global prioritisation systems including the International Union for Conservation of Nature Key Biodiversity Areas (KBAs) Standard. In this paper, we review the IPA rationale and progress on IPA identification to date, including the perceived limitations of the process and how these may be overcome. We then present a revised set of criteria for use globally, developed through the combined experiences of IPA identification over the past decade and a half and through a recent global consultation process. An overview of how the revised IPA criteria can work alongside the newly published KBA Standard is also provided. IPA criteria are based around a sound, scientific, global framework which acknowledges the practical problems of gathering plant and habitat data in many regions of the world, and recognises the role of peer reviewed expert opinion in the selection process. National and sub-national engagement in IPA identification is essential, providing a primary route towards long term conservation of key sites for plant diversity. The IPA criteria can be applied to the conservation of all organism groups within the plant and fungal kingdoms.

Early anthropogenic impact on Western Central African rainforests 2,600 y ago

Significance Modern human societies live in strongly altered ecosystems. However, anthropogenic environmental disturbances occurred long before the industrial revolution. About 2,600 y ago, a forest–savannah mosaic replaced dense rainforests in Western Central Africa. This rainforest crisis was previously attributed either to the impact of climate change or, to a lesser extent, to the expansion of Bantu peoples through Central Africa. A 10,500-y sedimentary record from Lake Barombi, Southwest Cameroon, demonstrates that the rainforest crisis was not associated with any significant hydrological change. Based on a detailed investigation of a regional archaeological database, we present evidence that humans altered the rainforest ecosystem and left detectable traces in the sediments deposited in Lake Barombi. A potential human footprint on Western Central African rainforests before the Common Era has become the focus of an ongoing controversy. Between 3,000 y ago and 2,000 y ago, regional pollen sequences indicate a replacement of mature rainforests by a forest–savannah mosaic including pioneer trees. Although some studies suggested an anthropogenic influence on this forest fragmentation, current interpretations based on pollen data attribute the ‘‘rainforest crisis’’ to climate change toward a drier, more seasonal climate. A rigorous test of this hypothesis, however, requires climate proxies independent of vegetation changes. Here we resolve this controversy through a continuous 10,500-y record of both vegetation and hydrological changes from Lake Barombi in Southwest Cameroon based on changes in carbon and hydrogen isotope compositions of plant waxes. δ13C-inferred vegetation changes confirm a prominent and abrupt appearance of C4 plants in the Lake Barombi catchment, at 2,600 calendar years before AD 1950 (cal y BP), followed by an equally sudden return to rainforest vegetation at 2,020 cal y BP. δD values from the same plant wax compounds, however, show no simultaneous hydrological change. Based on the combination of these data with a comprehensive regional archaeological database we provide evidence that humans triggered the rainforest fragmentation 2,600 y ago. Our findings suggest that technological developments, including agricultural practices and iron metallurgy, possibly related to the large-scale Bantu expansion, significantly impacted the ecosystems before the Common Era.

Allexis zygomorpha (Violaceae): A New Species from the Littoral Forest of Cameroon

The genus Allexis is known only from West and Central Africa (Jenik & Enti 1968). So far, only three species have been described (Melchior 1924). Revision of the Central African Violaceae (Achoundong 1997), and production of an account for Flore du Cameroun has revealed a fourth species, described here as Allexis zygomorpha. Further exploration of the littoral forest in Cameroon may yield yet more species in this genus.

Vepris bali (Rutaceae), a new critically endangered (possibly extinct) cloud forest tree species from Bali Ngemba, Cameroon

Abstract: Vepris bali is the first known species of Vepris in WC Africa with opposite, trifoliolate leaves and is further unusual for its long petiolules. Known only from Bali Ngemba Forest Reserve, a remnant of submontane forest under great pressure of degradation in the Bamenda Highlands of Cameroon, it may already be extinct due to tree cutting and agricultural incursions. Here, V. bali is compared with other endemic cloud forest Vepris of the Cameroon Highlands and is described, illustrated, mapped and assessed as Critically Endangered (Possibly Extinct) using IUCN 2012 criteria. Citation: Cheek M., Gosline G. & Onana J.-M. 2018: Vepris bali (Rutaceae), a new critically endangered (possibly extinct) cloud forest tree species from Bali Ngemba, Cameroon. - Willdenowia 48: 285–292. doi: https://doi.org/10.3372/wi.48.48207 Version of record first published online on 24 August 2018 ahead of inclusion in August 2018 issue.

Reply to Giresse et al.: No evidence for climate variability during the late Holocene rainforest crisis in Western Central Africa

Giresse et al. (1) criticize both our paleoclimatic reconstruction and our inferred anthropogenic origin of the late Holocene rainforest crisis (LHRC) (2). However, their argumentation, which is combined with alleged evidence for a climatic change during the LHRC, lacks strong support. Citing studies describing both brief (weeklong) and limited periods of leaf wax production in deciduous trees, Giresse et al. (1) conclude that leaf waxes cannot record the environmental variability of a full season. However, this argument is flawed, as evergreen and subtropical deciduous trees produce leaf waxes over much longer timescales—their δD (δDwax) values have been shown to capture environmental variability on even seasonal timescales (3, 4 … [↵][1]1To whom correspondence should be addressed. Email: yannickgarcin{at}yahoo.fr. [1]: #xref-corresp-1-1

Reply to Clist et al.: Human activity is the most probable trigger of the late Holocene rainforest crisis in Western Central Africa

Clist et al. (1) challenge our conclusions (2), criticizing our archaeological synthesis to maintain that the late Holocene rainforest crisis (LHRC) in Western Central Africa (WCA) was not triggered by human activity. Clist et al. (1) claim that the archaeological 14C dates we used were not critically evaluated, as we were more concerned with the quantity of dates rather than their quality. However, a careful reading of our article (2) and its associated SI Appendix unambiguously documents that we cautiously weighted the radiometric dates by applying a binning in space and time to correct for investigator bias and oversampling at different sites, following refs. 3⇓–5; this … [↵][1]1To whom correspondence should be addressed. Email: yannickgarcin{at}yahoo.fr. [1]: #xref-corresp-1-1