Centre for Ecosystem Science, University of New South Wales, Sydney, New South Wales, Australia.
NSW Department of Planning and Environment, Parramatta, New South Wales, Australia.
Conserv Biol. 2023 Feb;37(1):e13995. doi: 10.1111/cobi.13995. Epub 2022 Nov 21.
Insights into declines in ecosystem resilience and their causes and effects can inform preemptive action to avoid ecosystem collapse and loss of biodiversity, ecosystem services, and human well-being. Empirical studies of ecosystem collapse are rare and hampered by ecosystem complexity, nonlinear and lagged responses, and interactions across scales. We investigated how an anthropogenic stressor could diminish ecosystem resilience to a recurring perturbation by altering a critical ecosystem driver. We studied groundwater-dependent, peat-accumulating, fire-prone wetlands known as upland swamps in southeastern Australia. We hypothesized that underground mining (stressor) reduces resilience of these wetlands to landscape fires (perturbation) by diminishing groundwater, a key ecosystem driver. We monitored soil moisture as an indicator of ecosystem resilience during and after underground mining. After landscape fire, we compared responses of multiple state variables representing ecosystem structure, composition, and function in swamps within the mining footprint with unmined reference swamps. Soil moisture declined without recovery in swamps with mine subsidence (i.e., undermined), but was maintained in reference swamps over 8 years (effect size 1.8). Relative to burned reference swamps, burned undermined swamps showed greater loss of peat via substrate combustion; reduced cover, height, and biomass of regenerating vegetation; reduced postfire plant species richness and abundance; altered plant species composition; increased mortality rates of woody plants; reduced postfire seedling recruitment; and extirpation of a hydrophilic animal. Undermined swamps therefore showed strong symptoms of postfire ecosystem collapse, whereas reference swamps regenerated vigorously. We found that an anthropogenic stressor diminished the resilience of an ecosystem to recurring perturbations, predisposing it to collapse. Avoidance of ecosystem collapse hinges on early diagnosis of mechanisms and preventative risk reduction. It may be possible to delay or ameliorate symptoms of collapse or to restore resilience, but the latter appears unlikely in our study system due to fundamental alteration of a critical ecosystem driver. Efectos de las interacciones entre los estresantes antropogénicos y las perturbaciones recurrentes sobre la resiliencia y el colapso de los ecosistemas.
洞察生态系统弹性的下降及其原因和影响，可以为避免生态系统崩溃和生物多样性、生态系统服务以及人类福祉的丧失提供先发制人的行动。对生态系统崩溃的实证研究很少，并且受到生态系统复杂性、非线性和滞后响应以及跨尺度相互作用的阻碍。我们研究了人为压力源如何通过改变关键生态系统驱动因素来降低生态系统对反复扰动的弹性。我们研究了澳大利亚东南部依赖地下水、积累泥炭、容易发生火灾的湿地，称为旱地沼泽。我们假设，地下采矿（压力源）通过减少地下水（关键生态系统驱动因素）来降低这些湿地对景观火灾（扰动）的弹性。我们监测了土壤水分，作为监测生态系统弹性的指标，包括在地下采矿期间和之后。在景观火灾之后，我们比较了采矿足迹内的受矿区和未受矿区的多个代表生态系统结构、组成和功能的状态变量的响应。在有矿坑沉降（即被破坏）的沼泽中，土壤水分下降且没有恢复，但在 8 年内，参考沼泽中的土壤水分保持稳定（效应大小为 1.8）。与燃烧的参考沼泽相比，燃烧的被破坏的沼泽中通过基质燃烧损失了更多的泥炭；再生植被的覆盖、高度和生物量减少；火灾后植物物种丰富度和丰度减少；植物物种组成改变；木本植物死亡率增加；火灾后幼苗的补充减少；以及亲水动物的灭绝。因此，被破坏的沼泽表现出强烈的火灾后生态系统崩溃症状，而参考沼泽则强劲再生。我们发现，人为压力源降低了生态系统对反复扰动的弹性，使其易发生崩溃。避免生态系统崩溃取决于对机制的早期诊断和预防性风险降低。延迟或减轻崩溃的症状或恢复弹性可能是可行的，但在我们的研究系统中，由于关键生态系统驱动因素的根本改变，后者似乎不太可能。
