越南蝙蝠在環境變遷下的時空分布模式

Abstract

生物多樣性的喪失是當前社會的一項環境危機，對生態系和人類福祉造成巨大的衝擊。建立保護區是防止生物多樣性喪失和維護生態系統完整性最普遍的方式之一，但許多保護區規劃時未納入生物多樣性分布的時間與空間資訊導致成效不彰，且生物多樣性分布可能隨著環境變化而改變，進而影響現有保護區的保育成效。此外，許多保護區在規劃時受限於行政區界線的限制，無法有效涵蓋物種跨邊界的分布和遷移範圍，因此也限制了保護區的保育成效。在蝙蝠（翼手目）的保育上，因為牠們分布廣泛、對環境變化敏感、具良好移動能力，但卻不易觀察，使得保護區的制定更加困難。因此，我的研究以越南的蝙蝠為例，揭示如何取得並利用環境變遷下物種分布的時空資訊，用以研擬保育計劃的制定。具體來說，我分析蝙蝠物種的分布並預測牠們在氣候和土地覆蓋變化下的動態，以（1）瞭解這兩個主要環境變化各別和在交互作用下對蝙蝠所造成的影響，來指引保育策略的制定；（2）評估現有保護區網絡涵蓋蝙蝠分布範圍的代表性，並指出應優先考慮作為蝙蝠保護區的地點；以及（3）評估面對環境變化下，跨國合作對於決定蝙蝠保育優先保護區域的重要性。在我的博士論文的第一項研究中，我使用物種分布模型和不同溫室氣體排放和環境變化情境，預測了81種在越南出現的蝙蝠現今和未來的分布，評估氣候和土地覆蓋變化對於蝙蝠分布範圍和物種豐富度的影響。結果顯示直到2050年，這兩種威脅個別皆將對蝙蝠產生負面的影響，且當兩種威脅同時發生時，將會降低個別威脅的正面效應或增強個別威脅的負面效應，使整體負面影響加劇。此外，這兩項環境變化所造成的正負效應與程度在蝙蝠物種與地理區域上具有顯著變異，強調出將各別物種分布資訊納入蝙蝠保育規劃的重要性。

由於建立保護區是最普遍被使用的保育方式之一，因此在第二項研究中，我使用物種分布資訊來評估越南現有的保護區網絡對於保護蝙蝠分布範圍的代表性。我分別計算出現於越南的每種蝙蝠分布範圍中有多少比例位於現有的保護區當中，並以此作為保護代表性的評估標準。我發現儘管現有的保護區網絡比隨機網絡更具代表性，但它平均僅涵蓋了蝙蝠目前分布範圍的6.56％。若整合物種分布資訊與空間優先分析，在不增加網絡大小的情況下，調整現有保護區網絡的分布可以增加代表性至12.11％。結果也顯示將未來蝙蝠分布的預測納入保護區設置優先分析，並不會影響保護區對現今蝙蝠分布範圍的代表性，但可以顯著提升環境變化下，對未來蝙蝠分布的代表性。最後，物種分布模型顯示活動於越南的81種蝙蝠中有79種分布範圍超出越南的邊界，且氣候和土地覆蓋變化可能會影響牠們在越南內外的分布。因此，在第三項研究中，我以跨越越南、寮國和柬埔寨三國的範圍進行保護區設置優先分析（跨界優先），並相較於各國分別進行優先分析（國家優先）的結果，比較對於蝙蝠分布範圍的代表性何者為高。結果顯示，跨界優先和國家優先所建議的保護區網絡對於現今蝙蝠分布範圍具有相似的代表性，然而，在環境變化的情況下，特別是在考慮到蝙蝠未來分布的預測時，跨界優先能得到更好的結果，顯示跨國合作的重要性。

總結來說，以上研究說明了氣候和土地覆蓋變化的相互作用可能會對蝙蝠造成嚴重的負面影響。為了在環境變化下維持保育的有效性，在保護區規劃中納入蝙蝠分布的時空資訊與跨國界合作至關重要。此研究不僅增進了我們對於環境變化對蝙蝠多樣性潛在影響的理解，也提供了在保育上減緩衝擊的建議。本研究所建立的研究方法，特別是將物種的時空分布整合至設立跨國界保護區的考量之中，將可擴展應用於其他類群。

Biodiversity loss is an environmental crisis that causes huge impacts on ecosystems and human well-being. Establishing protected areas is one of the most common tools to prevent biodiversity loss and maintain ecosystem integrity. However, many protected areas perform poorly due to not incorporating spatiotemporal information on biodiversity distributions into the design. In particular, biodiversity distributions are likely to change in response to environmental changes, further affecting the effectiveness of current protected areas. In addition, many conservation efforts have limited effectiveness because planning is usually restricted by administrative boundaries, failing to capture species’ across-boundary distributions and movement. These challenges are particularly serious for bats (Order Chiroptera) because of their wide distributions, sensitivity to environmental changes, relatively good dispersal ability, and elusive nature. My study thus aims to use the bats in Vietnam as a case to demonstrate how the spatiotemporal information on species distributions under environmental changes can be obtained and used for guiding conservation planning. Specifically, I characterized bat species distributions and predicted their dynamics under projected climate and land-cover changes to (1) investigate the individual and interactive effects of the two major environmental changes on bats for guiding conservation strategies, (2) access the representativeness of the current protected area network for bats and identify prioritized areas to improve the representativeness, and (3) evaluate the importance of transboundary collaboration for prioritizing protected areas for bat conservation in the face of environmental changes.In the first study of my dissertation, I predicted current and future distributions of 81 bat species in Vietnam under different CO2 emission and environmental change scenarios using species distribution models. Evaluations of individual and interactive effects of climate and land-cover changes on the bats’ range size and species richness patterns revealed that both threats individually would predominantly exert negative effects by the 2050s. Furthermore, simultaneous occurrences of these threats would generally intensify the impacts by mitigating individual positive effects and/or enhancing negative effects. Because of significant interspecific and geographic variations in the direction and magnitude of these effects, my results underscore the importance of incorporating species-specific and spatial-explicit information on species distributions into conservation planning for bats.Since establishing protected areas is one of the most commonly used conservation approach, in the second study I used the information on species distribution to evaluate the representativeness of Vietnam’s current protected area network for bats. I calculated the proportion of individual bat species’ range within protected areas as a measure of the representativeness. I found that although the current network is more representative than random, it only covers, in average, 6.56% of the bats’ current distribution ranges. By integrating the species distribution information with a spatial prioritization analysis, I showed that the range coverage of the protected area network can increase to 12.11% without increasing the network’s size. While incorporating the predictions of future bat distributions into the prioritization process did not influence the current representativeness, it can significantly improve the representativeness under projected environmental changes.Finally, the species distribution models showed that 79/81 bat species have their distribution ranges beyond Vietnam’s boundary and climate and land-cover changes are likely to affect their distributions both inside and outside Vietnam. Therefore, in the third study I assessed whether the prioritization process implemented across Vietnam, Laos and Cambodia together (i.e., transboundary prioritization) can lead to higher representativeness of protected areas than the prioritization implementedwithin each of the countries independently (i.e., national prioritization). The results showed that the transboundary and national prioritization processes resulted in similar representativeness of protected areas under the current situation. However, transboundary prioritization had better performance under the changing environments, especially when the projected future distributions of bats were accounted for in the prioritization process.In summary, these studies show that climate and land-cover changes are likely to interactively cause profound negative impacts on bats. For effective conservation in the face of environmental changes, it is essential to incorporate the spatiotemporal information on bat distributions and cross-border collaboration into conservation planning. This study not only improves our understanding of the potential impacts of environmental changes on bat diversity, but also provides conservation suggestions for mitigating the impacts. The developed approaches, particularly the integration of spatiotemporal patterns of species distribution into prioritizing protected areas within and across borders, can have broader conservation applications for other taxa.