Ecosystems are complex and data-intensive systems, and the ecologists still struggle to understand them in an integrated manner. Models that miss key dynamics can possibly lead to fallacious conclusions about the ecosystem fate. To address these limits and encompass whole and realistic ecosystems, we develop here a qualitative model with the help of discrete-event models. This model, based on formal Petri nets, was able to integrate biotic, abiotic and human-related components (e.g. grazing) along with their processes into the same interaction network. The model was also able to grasp ecosystem development, as defined by sharp changes of the interaction network structure itself. Furthermore, the model was possibilistic and thus rigorously computed all possible ecosystem states reached after a specific (present-day) initial state. This innovative approach in ecology then allows to rigorously and exhaustively identifying all possible ecosystem trajectories and to study their impacts and outcomes. For the first time in a realistic ecosystem, we illustrated such discrete and qualitative models in the case study of temporary marshes in the Mediterranean part of France, the Camargue delta. The model demonstrated that when marshes are exposed to extensive grazing the presence of marsh heritage species (i.e. with a conservation value) is facilitated by opening up the vegetation through various trajectories. This supports the commonly used management practices of extensive grazing to conserve certain protected habitats. The detailed analysis of the computed ecosystem trajectories allows exploring a range of recommendations for management strategies.

生态系统是复杂且数据密集的系统，生态学家仍然难以以一种综合的方式来理解它们。缺少关键动态的模型可能会得出关于生态系统命运的谬误结论。为了解决这些限制并涵盖整个和现实的生态系统，我们在此借助离散事件模型开发定性模型。该模型基于正式的Petri网，能够将生物，非生物和人类相关成分（例如放牧）及其过程集成到同一交互网络中。该模型还能够把握生态系统的发展，这是由相互作用网络结构本身的急剧变化所定义的。此外，该模型是可能的，因此可以严格计算在特定（当前）初始状态之后达到的所有可能的生态系统状态。然后，这种创新的生态方法可以严格，详尽地识别所有可能的生态系统轨迹，并研究其影响和结果。在现实的生态系统中，我们首次在法国地中海地区Camargue三角洲的临时沼泽案例研究中阐述了这种离散和定性的模型。该模型表明，当沼泽地遭受广泛放牧时，通过各种轨迹开放植被可以促进沼泽遗产物种（即具有保护价值）的存在。这支持了广泛放牧的常用管理方法，以保护某些受保护的栖息地。对计算出的生态系统轨迹的详细分析可以探索一系列有关管理策略的建议。