Sanjiangyuan National Park is the first pilot of the national park system in China. It requires the strictest ecological protection. At the same time, the relationship between the local pastoralists’ livelihood and the carrying capacity of resources and environment should be properly handled to form a new model of harmonious development between humans and nature. This study explores the nature proportion (N%), i.e., the minimum conservation area for biodiversity and ecosystem services and the maximum area for local pastoralists’ livelihood at the regional scale of the Sanjiangyuan National Park, and seeks approaches and models of sustainable management of the social-ecological system. The theoretical, realized and predicted N% are calculated based on: the diet niche volume and overlap of domestic livestock (Domestic yak and Tibetan sheep) and wild ungulate herbivores (Tibetan antelope, Tibetan gazelle, Wild yak and Tibetan wild ass), the population, density and land use of dominated livestock (116.70 × 10⁴ sheep unit) and wild ungulate herbivores (31.40 × 10⁴ sheep unit), and the livestock population (123.07 × 10⁴ sheep unit) at local (6.43 × 10⁴) pastoralists’ basic living needs, by 90%, 30 % and 74%, respectively. Furthermore, the realized and predicted N% can be optimized to 67 and 83%, respectively, by spatial coupling and optimizing of resource allocation among regions, and utilizing forage resources produced by the development of the grass industry in the peripheral support area for “Rest grazing during turning green period” and “Warm Grazing Cold Feeding Two-stage Feeding” (supplying forage for 190 days, i.e., an increase of 4.47 × 104 km² grassland for conservation) or for livestock population

(feeding livestock of 60.25 × 10⁴ sheep unit, i.e., increase of 1.55 × 10⁴ km² grassland for conservation) at local pastoralists’ basic living needs. The N% obtained by different accounting conditions, methods, and purposes is quite different. The accounting of a practical and reasonable N% under multiple targets should consider identifying, prioritizing and zoning of biodiversity conservation areas, key areas of ecological security barriers, the areas offsetting the impact of future climate change, the beneficiary areas of important ecosystem services (such as water resources), suitable areas for local pastoralists’ development, and ecosystem services assessment and quantifying of ecosystem services goods. By identifying and comprehensive consideration of all of the above factors affecting the social-ecological system, it is possible to quantify N% for Sanjiangyuan National Park at a scale of ecoregions, so as to realize its sustainable development.

三江源国家公园是我国第一个体制试点的国家公园，要求实行最严格的生态保护，同时要处理好当地牧民生计与资源环境承载能力的关系，形成人与自然和谐发展新模式。本文就该国家公园所在地区区域尺度上生物多样保护最小面积与民生需求最大面积相协调的自然比例进行了探索，寻求可持续管理的途径与模式。通过国家公园区域内家畜（家牦牛Bos grunniens和藏系绵羊Ovis aries）和主要野生有蹄类草食动物（藏羚Pantholops hodgsonii、藏原羚Procapra picticaudata、野牦牛B. mutus和西藏野驴Equus kiang）的营养生态位体积和重叠，现有家畜和主要野生有蹄类草食动物的数量（分别为116.70 × 10⁴和31.40 ×  10⁴羊单位），保障当地牧民（6.43 × 10⁴人）基本生活需求的家畜存栏量（123.07 × 10⁴羊单位）等核算出该国家公园需要保护的自然区域面积最低比例，即自然比例（Nature Proportion, N%），其理论值、现实值和预期值分别为90%、30%和74%。通过区域资源空间配置优化，将外围支撑区发展草产业生产的饲草资源用于“返青期休牧”和“暖牧冷饲两段式养殖”模式（可供饲养190d所需饲草，即增加保护草地4.47 × 104 km²），或用于满足当地牧民基本生活需求的家畜（可饲养60.25 × 10⁴羊单位，即增加保护草地1.55 ×10⁴ km²）等优化了该国家公园N%的现实值和预期值，分别为67%和87%。不同的核算条件、方法和目的得到的N%存在较大差异。多重目标下的三江源国家公园N%的核算，应考虑：生物多样性保护优先区域识别、生态安全屏障重点区域识别、应对未来气候变化影响保护区域识别及重要性区分、重要生态系统服务（如水资源）受益区域识别、当地牧民群众发展适宜区域识别及优先性区分、生态系统服务评估和生态系统服务商品供给量核算，合理核算三江源国家公园所在区域的N%，从而实现社会—生态系统可持续管理。