Um novo ecossistema: florestas urbanas construídas pelo Estado e pelos ativistas

abstract Historically, the expansion of cities resulted in the replacement of natural landscape by urban environments, resulting in environmental degradation through changes in soil cover, hydrological systems, biogeochemical cycles, biodiversity, making cities particularly vulnerable to climate changes. Environmental restoration in cities is a measure to promote life quality, and urban forests play a key role in restoring the quality of the urban environment. They provide valuable ecosystem services for maintaining biodiversity, ensuring human health, and social well-being. As everyone has the right to live in a balanced, healthy and common use environment essential to suppor quality of life, urban green areas are an interdisciplinary issue of collective concern. It is the responsibility of the government to regulate, plant and manage urban trees in order to standardize urban afforestation by planting trees at predetermined distances according to the size of each species. However, the vacuum in the greening process left by the State is being filled by activists who, in general, use a different protocol that aims at higher tree density based on the notion of ecological succession. By promoting the restoration of ecosystem services, both initiatives tend to bring significant benefits to large cities such as São Paulo. However, the complexity of the urban landscape requires a systemic evaluation of tree planting to define spatial adequacy and optimize benefits. The planting of urban forests should not aim to recreate pre-urban natural conditions, but rather to develop green areas integrated to the urban network that guarantee a healthy and balanced environment while preserving social interactions. By perceiving the urban environment as a complete ecosystem, it is possible to establish criteria that optimize the benefits of urban afforestation. These criteria should be based on technical and scientific knowledge, and take into account social needs, so that the best method is chosen on a case-by-case basis.

摘要 历史上，城市扩张以建成环境取代自然景观，通过改变土壤覆盖、水文系统、生物地球化学循环与生物多样性引发环境退化，使得城市尤其易受气候变化影响。城市环境修复是提升生活品质的重要举措，而城市森林在改善城市环境质量方面发挥关键作用。它们为维持生物多样性、保障人类健康与社会福祉提供了宝贵的生态系统服务。鉴于人人均有权享有支撑优质生活所需的均衡、健康且可共同使用的环境，城市绿地成为跨学科且受集体关注的议题。规范城市绿化、依据各物种的规格以预设间距种植树木并开展管护，是政府的职责所在。然而，政府在绿化进程中留下的空白，正由环保行动者填补——这类群体普遍采用基于生态演替理念、旨在实现更高树木密度的不同实施规程。通过推动生态系统服务的修复，上述两类举措均有望为圣保罗等大城市带来显著收益。但城市景观的复杂性要求对植树工作开展系统性评估，以明确空间适配性并优化综合效益。城市森林的营造不应以重建城市开发前的自然状态为目标，而应打造与城市网络融为一体的绿地空间，在保障社会互动的同时，营造健康均衡的人居环境。若将城市环境视为完整的生态系统，便可确立优化城市绿化效益的评判标准。此类标准应基于技术与科学知识，并兼顾社会需求，从而能够按需选择最优实施方法。