Safeguarding Imperiled Biodiversity and Evolutionary Processes in the Wallacea Center of Endemism

Abstract

Wallacea-the meeting point between the Asian and Australian fauna-is one of the world's largest centers of endemism. Twenty-three million years of complex geological history have given rise to a living laboratory for the study of evolution and biodiversity, highly vulnerable to anthropogenic pressures. In the present article, we review the historic and contemporary processes shaping Wallacea's biodiversity and explore ways to conserve its unique ecosystems. Although remoteness has spared many Wallacean islands from the severe overexploitation that characterizes many tropical regions, industrial-scale expansion of agriculture, mining, aquaculture and fisheries is damaging terrestrial and aquatic ecosystems, denuding endemics from communities, and threatening a long-term legacy of impoverished human populations. An impending biodiversity catastrophe demands collaborative actions to improve community-based management, minimize environmental impacts, monitor threatened species, and reduce wildlife trade. Securing a positive future for Wallacea's imperiled ecosystems requires a fundamental shift away from managing marine and terrestrial realms independently.

Keywords: applied ecology; conservation; evolution; interdisciplinary science; tropical ecosystems.

Figure 1.

Maps of Wallacea showing its location in Southeast Asia (a), zones of endemism on land (b) and in coastal marine environments (c). See supplemental tables S1 and S2 for further information on the zones. In panel (b), the shading represents Indonesia's primary forest cover in 2018 compiled from Margono and colleagues (2014) and data from www.globalforestwatch.org. Forest according to this definition cannot be reproduced consistently for Timor-Leste, so forest is not displayed for this country. Forests are also difficult to map consistently in the drier parts of Wallacea, notably the Lesser Sunda islands (Nusa Tenggara); see box 1. In panel (c) mangrove cover (green/dark shading) is derived from Bunting and colleagues (2018) and corals (orange/light shading) from https://allencoralatlas.org.

Figure 2.

Patterns of terrestrial endemism—as inferred by range restricted reptile, mammal, bird, and amphibian species in the IUCN database—for the eight zones presented in figure 1. Zones are outlined by Michaux (2010) and expanded to include other areas of Sulawesi (figure 1; table S1). Each plot shows the proportion of terrestrial vertebrate species that are range restricted according to www.iucnredlist.org. The assessment is limited to those taxa formally recognized as species and so may underrepresent endemism within species complexes, particularly in parts of Sulawesi (figure 3) and along the island chains of Nusa Tenggara. The shaded background to each plot denotes the percentage of land forested in 2019, and pie charts indicate progress made in each region (percentage in orange or light shade) to meet the country's target of protecting 17% of land by 2020 (based on IUCN categories I–IV for protected areas from www.protectedplanet.net).

Figure 3.

The origins of Sulawesi and some of the resulting contact zones among endemic species or populations in Sulawesi as determined using genetic data. Examples of separated taxa include macaque (Macaca spp.), tarsier (Tarsius spp.), and gliding lizard (Draco spp.). Divergent subpopulations include the Celebes toad (Ingerophrynus celebensis), babirusa (Babyroussa celebensis), and swift fruit bat (Thoopterus nigrescens). Schematic based on Nugraha and Hall (2018). Photographs: Sulawesi babirusa from Simon Mitchell; swift fruit bat Klaus Rudloff; other images from Wikimedia commons.

Figure 4.

Livelihood systems, cultivated crops and mining commodities in Wallacea compared with other parts of Indonesia. In panel (a), the primary livelihoods at the village level are shown according to Indonesia's Village Potential census in 2018. Subsistence livelihoods include subsistence agriculture, swidden agriculture, hunting and gathering of forest products and capture fisheries; market-orientated livelihoods include monoculture, horticulture, logging, animal breeding, aquaculture, and commercial fisheries. Western Indonesia includes Java, Sumatra, and Kalimantan; Wallacea 
is Sulawesi, Maluku and Nusa Tenggara; Eastern Indonesia includes Papua, West Papua and nearby islands. Panel (b) shows the total cultivated area of the 10 dominant agricultural commodities in Wallacea and Indonesia more widely, according to the Directorate General of Estate Crops Indonesia in 2019. Panel (c) shows the total concession area under production for the 10 most dominant mineral commodities in Wallacea a decade before and after mining policy changes 
in 2010, according to the Ministry of Energy and Mineral Resources.

Figure 5.

Forest and forest uses in Wallacea. (a, b) Agroforestry practiced in community managed forest of Seram, Maluku raises the question of how to define a forest from aerial imagery. (c, d) Seasonal forests in Sumbawa, Nusa Tenggara are mostly deciduous and fragmented by small-scale agriculture. (e, f) Examples of the many uses of forests for local communities include timber extraction (in the present figure, Seram, Maluku) and subsistence hunting (Flores, Nusa Tenggara). Photographs: Aris Santaya (a), Ulat Ifansasti (b, e) and Aulia Erlangga (c, f), courtesy of CIFOR.org, and Gemma Bramley (d), Royal Botanic Gardens Kew.

Figure 6.

Intact (a) and degraded (b) coral reef in North Sulawesi, and 2 years of restoration in Spermonde, South Sulawesi (c). Old growth (d) and degraded (e) mangrove forests in North Sulawesi, followed by community-based hydrological restoration (f)—that is, a channel that was reopened to connect the old shrimp pond area to the sea. Photographs: Maarten De Brauwer (a, b), Dominic Muenzel (c), Karen Diele (d, e), Rignolda Djamaluddin (f).