Data from: Targeted reforestation could reverse declines in connectivity for understory birds in a tropical habitat corridor

Re-establishing connectivity between protected areas isolated by habitat
clearing is a key conservation goal in the humid tropics. In northeastern
Costa Rica, payments for environmental services (PES) and a government ban
on deforestation have subsidized forest protection and reforestation in
the San Juan–La Selva Biological Corridor (SJLSBC), resulting in a decline
in mature forest loss and the expansion of tree plantations. We use field
studies and graph models to assess how conservation efforts have altered
functional connectivity over the last 25 years for four species of
insectivorous understory birds. Field playback studies assessed how
reforestation habitat quality affected the willingness of Myrmeciza exsul,
Henicorhina leucosticta, Thamnophilus atrinucha, and Glyphorynchus
spirurus to travel outside forest habitat for territorial defense.
Observed travel distances were greatest in nonnative and native tree
plantations with high understory stem density, regardless of overstory
composition. In contrast, tree plantations with low stem density had
travel responses comparable to open pasture for three of the four bird
species. We modeled landscape connectivity for each species using graph
models based on varying possible travel distances in tree plantations,
gallery forests, and pastures. From 1986 to 2011, connectivity for all
species declined in the SJLSBC landscape (5825 km2) by 14% to 21% despite
only a 4.9% net loss in forest area and the rapid expansion of tree
plantations over 2% of the landscape. Plantation placement in the
landscape limited their potential facilitation of connectivity because
they were located either far from forest cover or within already
contiguous forest areas. We mapped current connectivity bottlenecks and
identified priority areas for future reforestation. We estimate that
reforestation of priority areas could improve connectivity by 2% with only
a 1% gain in forest cover, an impressive gain given the small area
reforested. Results indicate key locations where spatial targeting of PES
within the SJLSBC study region would protect existing forest connectivity
and enhance the connectivity benefits of reforestation.

恢复因栖息地开垦而隔离的保护区之间的连通性，是湿润热带地区的核心保护目标。在哥斯达黎加东北部，环境服务付费（Payments for Environmental Services, PES）政策与政府禁伐令，为圣胡安-拉塞尔瓦生物走廊（San Juan–La Selva Biological Corridor, SJLSBC）内的森林保护与再造林提供了补贴，使得成熟林流失量下降，人工林面积快速扩张。本研究依托野外调查与图论模型，评估了过去25年间，保护举措如何改变了4种食虫林下鸟类的功能连通性。野外鸣声回放实验探究了再造林栖息地质量对黑喉蚁鸟（Myrmeciza exsul）、白胸林鹩（Henicorhina leucosticta）、黑顶蚁鵙（Thamnophilus atrinucha）与条纹蚁鵙（Glyphorynchus spirurus）离开森林栖息地开展领域防御的意愿的影响。观测结果显示，无论林冠层组成如何，林下茎秆密度较高的外来与本土人工林，其鸟类移动距离最远。与之形成对比的是，对于4种鸟类中的3种而言，茎秆密度较低的人工林，其诱导的移动响应与开阔牧场并无显著差异。本研究基于人工林、走廊林与牧场中不同的潜在移动距离，通过图论模型为每个物种构建了景观连通性模型。1986年至2011年间，尽管SJLSBC研究区（面积5825平方千米）的森林净流失仅为4.9%，且人工林面积扩张至占全区2%，但所有物种的连通性均下降了14%至21%。人工林在景观中的布局限制了其对连通性的潜在促进作用——这些人工林要么距离森林覆盖区过远，要么本身就处于已经连片的森林区域内。本研究绘制了当前的连通性瓶颈区域，并确定了未来再造林的优先区域。我们估算，优先区域的再造林仅需使森林覆盖率提升1%，即可将连通性改善2%；在再造林面积如此有限的情况下，这一增益效果相当显著。研究结果明确了SJLSBC研究区内的关键区位，在此类区域针对性实施环境服务付费政策，既能保护现有森林连通性，也能强化再造林带来的连通性增益效应。