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Colonialism has disrupted Indigenous socioecological systems around the globe, including those supported by intentional landscape burning. Because most disruptions happened centuries ago, our understanding of Indigenous fire management is largely inferential and open to debate. Here, we investigate the ecological consequences of the loss of traditional Aboriginal fire management on fire-exposed savannas on the Arnhem Plateau, northern Australia, using the fire-sensitive conifer Callitris intratropica as a bio-indicator. We contrast Kakadu National Park, where traditional Aboriginal fire management was severely disrupted during the early twentieth century following Aboriginal relocation to surrounding settlements, and an adjacent Aboriginal estate where traditional Aboriginal fire management endures. Since 2006, traditional Aboriginal fire management at this site has been overlaid by a program of broad-scale institutionalized burning in the early dry season, designed to reduce greenhouse emissions. Using remote sensing, field survey, and dendrochronology, we show that on the Aboriginal estate, C. intratropica populations depend on the creation of a shifting patch mosaic of long unburned areas necessary for the recruitment of C. intratropica. However, the imposition of broad-scale fire management is disrupting this population patch dynamic. In Kakadu, there have been extreme declines of C. intratropica associated with widespread fires since the mid twentieth century and consequent proliferation of grass fuels. Fire management in Kakadu since 2007, designed to increase the size and abundance of patches of unburned vegetation, has not been able to reverse the population collapse of C. intratropica. Our study demonstrates that colonial processes including relocation of Indigenous people and institutional fire management can have deleterious consequences that are nearly irreversible because of hysteresis in C. intratropica population dynamics. [ABSTRACT FROM AUTHOR]

Understanding how novel biotic interactions can affect the persistence of plant and animal populations is of critical conservation concern. Rodents have been introduced to most oceanic islands and predate a wide range of seeds. However, little research has evaluated their effects on the long-term viability of plant populations. We assess the effects of seed predation by introduced rodents on the demography of three long-lived, common native trees in a Hawaiian forest. Using a 17-year demographic dataset, we assess if populations are viable under standard forest conservation practices; then we explore the potential effects of reducing seed predation by non-native organisms, reducing non-native understory cover, or reducing both, on population growth. Post-dispersal seed removal ranged from 40 to 98 % and increased as a function of understory cover. Survival was low for seedlings due to competition from non-native understory plants. Sixty-two percent of Pysdrax odorata seeds suffered pre-dispersal predation by an introduced moth and 72 % of Nestegis sandwicensis seeds were prematurely aborted. Integral projection models show that λ values under standard conservation were <1, indicating population decline. Reducing seed predation by introduced rodents had a strong positive effect on λ for Diospyros sandwicensis , but the effect was much smaller for the other two species. Seed predation by introduced rodents can drive slow population decline of common native trees even in areas actively managed for conservation. Further, reducing rodent predation alone is likely insufficient to ensure long-term persistence due to additional bottlenecks in viable seed production. More attention to common tree species on oceanic islands is critical. • We assess how seed predation by introduced rodents affects demography of trees. • Seed removal increased with increasing understory vegetation cover. • Reducing seed predation increased population growth for one tree species. • For two other species, other bottlenecks in seed production led to limited impacts. • Many common tree species on islands are likely declining, even under conservation. [ABSTRACT FROM AUTHOR]