干旱加剧了人兽冲突，迫使食肉动物更靠近人类居住地。

加州干旱时期人兽冲突显著增加，其中对食肉动物的影响最为显著。冲突报告数量随降水量减少而上升，并在一年中最温暖、最干燥的月份达到高峰。

　　

最新研究表明，降雨量减少加剧了人与野生动物（尤其是食肉动物）的接触，揭示了干旱如何重塑加利福尼亚州的生态和人类行为。

研究表明：干旱时期人兽冲突加剧。图片来源：JoeFotos / Shutterstock

最近发表在《科学进展》（Science Advances）杂志上的一项研究中 ，研究人员探讨了干旱对人兽冲突的影响。人与野生动物之间的互动日益频繁，这对保护项目构成了根本性的挑战。随着人兽冲突的持续存在，深入了解气候变化如何影响资源可利用性和人兽冲突动态，对于预测未来社会生态系统的变化至关重要。

干旱如何改变野生动物资源利用

干旱是气候变化的常见表现形式，对野生动物和人类都造成了压力。虽然干旱会限制野生动物在荒野地区的资源获取，但人类的基础设施往往能缓解干旱的影响，吸引野生动物前来寻求人为的资源。因此，由于资源共享的重叠和竞争加剧，人兽冲突的可能性也会增加。然而，干旱与冲突加剧之间具体的行为和生态机制尚不明确，本研究强调，这些关联并不等同于因果关系，因为它们反映的是相关性，而非已证实的行为转变。

用于分析冲突趋势的数据来源

在本研究中，研究人员调查了干旱对人兽冲突的影响。他们利用了加州鱼类和野生动物管理局的野生动物事件报告（WIR）数据库，该数据库包含了2017年至2023年的人兽冲突事件报告。报告的事件涵盖了四大类广泛的互动：捕食、一般滋扰、潜在的人兽冲突和目击事件。

“气候变化将增加人与野生动物的互动，随着干旱和野火愈发极端，我们必须规划与野生动物共存的方式，”论文第一作者肯德尔·卡尔霍恩说道。他是加州大学戴维斯分校贾斯汀·史密斯实验室 和 加州大学洛杉矶分校廷格利 生态与保护实验室的成员。“动物进入人类活动区域通常被认为是野生动物试图从人类那里获取资源，但这往往是因为我们剥夺了野生地区的资源。”

Incident Categories Linked to Conflict Severity

The team primarily focused on two categories most likely associated with negative interactions, general nuisance, and depredation. The state of California was divided into 50 km by 50 km grid cells for analysis, and reported conflicts within each cell and month were compared with environmental covariates. Environmental covariates included seasonality (month), precipitation, human population density, median household income, and habitat structure (tree cover).

Modeling Drought Effects With Bayesian Methods

A hierarchical Bayesian modeling framework was adopted to investigate how changes in precipitation and other covariates affect incident frequency. In one model, incident reports for all species were treated agnostically and modeled together. Further, a separate set of diet-specific models was developed to explore whether these effects varied by species and diet guilds, where species were modeled under a shared diet-group hyperparameter.

Comparing Environmental Drivers Across Conflict Types

The influence of each environmental covariate on the frequency of conflict reporting across the four categories was also compared. In addition, three models investigated species-specific responses and the impact of diet on trends in reported conflicts, one for each diet group: carnivores, herbivores, and omnivores. In these species analyses, reports of species with more than 40 reported conflicts were included. The authors also noted that reporting patterns are partly shaped by human behavior and perceptions, which may influence how often conflicts are reported rather than how frequently they actually occur, because shifts in human activity, visibility, and willingness to report can contribute to observed trends.

Drought-Linked Conflict Increases Across California

The WIR database comprised 31,904 incident reports in California between 2017 and 2023. Most reports (57.2%) were related to depredation. The researchers found a significant increase in the number of wildlife conflicts associated with reductions in precipitation. Every 25 mm decrease in annual precipitation increased the frequency of reported incidents by 2.11%.

Habitat and Socioeconomic Factors Intensifying Conflict

Further, higher tree cover, higher human population density, and higher median household income, as well as areas with both higher human population density and tree cover, were associated with increased conflict reporting. Independently, depredation, general nuisance, and potential human conflict were negatively associated with precipitation. Notably, reported incidents showed the highest increase with decreased precipitation for carnivores.

Carnivore Sensitivity to Drought-Driven Resource Shortages

Importantly, decreased precipitation was a strong predictor of conflict reporting for carnivores, but not for herbivores or omnivores at the diet-guild level, clarifying that the earlier effects for carnivores remained robust at the species level rather than the guild-level aggregate. Species-specific analyses revealed significant increases in reported conflicts, accompanied by reduced precipitation, for three carnivores (mountain lions, bobcats, and coyotes) and one omnivore (American black bears). This distinction highlights that drought sensitivity is strongest for particular species rather than all members of a diet group.

Species-Level Conflict Rates Under Drought Stress

The number of conflicts increased for every 25 mm reduction in precipitation by 2.97 percent for bobcats, 2.56 percent for American black bears, 2.21 percent for coyotes, and 2.11 percent for mountain lions. Finally, the team investigated whether the frequency of conflict reporting varied with intra-annual drought periods and found that trends in reported incidents sharply increased during the driest and warmest months of the year (May to October) for eight species. These seasonal increases occurred independently of year-to-year precipitation trends, reflecting both ecological and human behavioral patterns, such as greater outdoor activity and higher wildlife detectability during summer months, as well as reduced water availability during peak drought periods.

Conservation Implications of Climate-Enhanced Conflict

Taken together, the results underscore that climate change may have significant ramifications for the future of conservation and human-wildlife conflict. The finding that lower precipitation is associated with conflict warrants investigations into how exactly drought affects space use and behavior for human and wildlife communities. The results also showed that carnivores experienced nearly three times the effect of drought as herbivores.

Seasonal Drought Patterns Shaping Conflict Risk

Further, season was a robust determinant of conflict reporting, and this effect is likely replicable in regions where intra-annual water availability influences human-wildlife interactions. While the impact of ongoing droughts may perturb animal behavior year-round, their effects are likely to be most pronounced when precipitation is at its seasonal low. The study also emphasizes that reporting patterns may be influenced by socioeconomic factors, cultural norms, and willingness to report conflicts, suggesting that the observed increases may reflect both ecological responses and human behavioral changes during drought conditions, including shifts in recreation timing, resource use, and opportunities for human-wildlife encounters. Overall, the study provides crucial empirical evidence on the amplification of human-wildlife conflict by climate change.

卡尔霍恩说：“我一直在寻找改善人与野生动物互动方式的方法，而气候变化会让这条路更加艰难。但如果我们能让情况变得更糟，那么我们也能让它变得更好。人们只需要对当地环境投入更多精力，保护工作就能奏效。”