1. Groundwater and surface water‐fed systems act as biodiversity hotspots and ecological refuges and evolutionary refugia in arid regions. Groundwater‐dominated systems are sustained by underground aquifers that are recharged by rain that has fallen in the distant past, while surface water‐dominated systems are fed by recent local rain or floods. Some waterbodies are fed by a mixture of these sources. Perennial, groundwater‐dominated systems will act as refuges and refugia under future rainfall declines associated with global warming. We sought to identify climate refugia, based on groundwater dominance, by using isotope hydrology to characterise water samples collected by citizen scientists across arid central Australia.
2. There is a linear relationship between hydrogen isotopes (²H/¹H, δ²H) and oxygen isotopes (¹⁸O/¹⁶O, δ¹⁸O) in rainfall. This relationship is known as the meteoric water line (MWL). By comparing our samples with the Australian MWL, and developing a local evaporation line, we were able to test the hypotheses that groundwater‐dominated systems will follow the Australian MWL while temporary systems follow the local evaporation line, and, accordingly, distinguish between groundwater and surface water‐dominated systems. The isotopic composition of samples collected over a 36‐month period was determined using isotope ratio infrared spectrometry. The electrical conductivity of each sample was recorded to determine where freshwater is available for biota within this arid region.
3. Over 240 water samples were collected from 62 waterbodies and seven bores (groundwater wells) spanning an area of more than 250,000 km². Approximately 75% of the samples were collected by citizen scientists and 25% by research scientists.
4. Twenty groundwater‐dominated waterbodies, characterised by a small range of δ²H and δ¹⁸O values (c. −55 to −20‰ and c. −9 to −3‰, respectively) clustered around the long‐term mean composition of rainfall (δ²H = −37.5‰, δ¹⁸O = −6.4‰), were identified as future evolutionary refugia. These sites are likely to contain water through the most severe of droughts and will be critically important for the persistence of water‐dependent species.
5. Based on their isotopic composition, we identified 45 waterbodies (rockholes/waterholes) as temporary or ephemeral (δ²H c. −40 to −100‰ and δ¹⁸O c. −4 to +25‰), that is, with no evidence of groundwater inflow. These, together with waterbodies supported by a mix of groundwater and surface water, can act as stepping stones and form part of the aquatic mosaic that is critical to supporting species in arid regions. Over two‐thirds of the waterholes sampled were very fresh (electrical conductivity <0.8 mS/cm), indicating that they provide the freshwater needed to support much of the regional aquatic and terrestrial fauna.
6. All evolutionary refugia are located within protected areas (i.e. national parks or Indigenous Protected Areas), but some are subject to the impacts of feral animal species and invasive plants. Our findings indicate where control programmes and restoration actions can be prioritised to support biodiversity conservation and climate change adaptation. Our approach, combining citizen science and isotope hydrology, can be used to identify future refugia in other remote and arid regions where water scarcity is likely to increase under global climate change.

中文翻译：

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利用公民科学和同位素水文学确定偏远干旱地区的地下水喂养气候避难所

1. 干旱地区的地下水和地表水系统是生物多样性的热点，生态避难所和进化避难所。地下水为主的系统由地下蓄水层维持，地下蓄水层由遥远的过去的降雨补充，而地表水为主的系统则由最近的局部降雨或洪水给水。一些水体由这些来源的混合物喂养。在与全球变暖有关的未来降雨减少的情况下，多年生的，以地下水为主导的系统将充当避难所和避难所。我们试图通过利用同位素水文学对澳大利亚中部干旱地区的公民科学家收集的水样进行表征，从而根据地下水的优势来确定气候变迁。
2. 有一个线性的氢同位素之间（关系² H / ¹ H，δ ² H）和氧的同位素（¹⁸ O / ¹⁶ O，δ ¹⁸O）在降雨中。这种关系称为流水线（MWL）。通过将我们的样本与澳大利亚MWL进行比较，并开发了一条局部蒸发线，我们能够检验以下假设：以地下水为主导的系统将遵循澳大利亚MWL，而临时系统将遵循本地蒸发线，从而区分地下水和地下水。地表水为主的系统。使用同位素比红外光谱法确定了在36个月内收集的样品的同位素组成。记录每个样品的电导率以确定该干旱区域内哪里有淡水可用于生物群。
3. 从62个水体和7个钻孔（地下水井）中收集了240多个水样，面积超过250,000 km ²。大约75％的样本是由公民科学家收集的，而25％是由研究科学家收集的。
4. 二十地下水为主的水体，其特征在于，在小范围的δ ² H和δ ^18个（O值Ç -55至-20‰和Ç分别-9至-3‰，）周围的长期平均组成群集雨量（δ ² H = -37.5‰，δ ¹⁸ O = -6.4‰），被确定为未来的进化避难所。这些地点在最严重的干旱中很可能含有水，对于持久依赖水的物种至关重要。
5. 基于它们的同位素组成，我们确定水体45（rockholes /水潭）为临时或短暂的（δ ² ħ  Ç -40到-100‰和δ ¹⁸ ö  Ç。-4〜+ 25‰），也就是，没有地下水流入的证据。这些以及结合有地下水和地表水的水体可以充当垫脚石，并构成水生马赛克的一部分，这对于在干旱地区支持物种至关重要。采样的水坑中有三分之二以上非常淡（电导率<0.8 mS / cm），这表明它们提供了支持大部分区域水生和陆生动物所需的淡水。
6. 所有进化避难所均位于保护区（即国家公园或土著保护区）内，但其中一些受到野生动物物种和入侵植物的影响。我们的发现表明，可以优先安排控制计划和恢复措施，以支持生物多样性保护和适应气候变化。我们的方法将公民科学和同位素水文学相结合，可用于确定其他偏远和干旱地区未来的避难所，在全球气候变化下水资源短缺可能会加剧。