Private land conservation areas (PLCAs) are increasingly looked to for meeting the deficit left by state-owned protected areas in reaching global conservation targets. However, despite the increasing extent and recognition of PLCAs as a complementary conservation strategy, little research has been done to quantify their effectiveness; a critical consideration if they are to be counted towards international biodiversity conservation targets. The long history of PLCAs in South Africa provides an interesting case study to address this knowledge gap. Here, we quantified the effectiveness of South African PLCAs by comparing losses in natural land cover and biodiversity intactness within PLCAs with different levels of protection to that of unprotected control points. Points within PLCAs were matched with unprotected control points to test the prediction that if PLCAs offer effective protection, losses in natural land cover and biodiversity intactness would be significantly lower within their boundaries in comparison to unprotected controls exposed to similar conditions. Consequences of natural land cover loss on biodiversity intactness were thus assessed, thus advancing standard approaches for quantifying effectiveness. Between 1990 and 2013, PLCAs lost significantly less natural land cover (3%) and biodiversity intactness (2%) than matched unprotected areas (6% and 4%, respectively). Of the natural land cover lost within PLCAs, most was converted to cultivated land. Farms can support more species than other land uses (e.g. mines), a likely explanation for why losses in biodiversity intactness were less than losses in natural land cover. Contrary to the predicted pattern, effectiveness did not increase with level of protection; informal PLCAs with no legal protection had comparable natural land cover and biodiversity intactness retention to strictly protected PLCAs, with most losses recorded among PLCAs with moderate protection. This study provides the first national-scale evidence that PLCAs can be an effective mechanism for conserving natural land cover and biodiversity intactness, which is highly relevant given current discussions around their likely long-term biodiversity conservation capacity.

越来越多地寻求私有土地保护区（PLCA）来弥补国有保护区在实现全球保护目标方面的不足。然而，尽管PLCA作为一种补充保护策略的范围越来越广，并被人们认可，但很少进行量化其有效性的研究。是否将其计入国际生物多样性保护目标至关重要。南非PLCA的悠久历史为解决这一知识鸿沟提供了有趣的案例研究。在这里，我们通过比较具有不同保护等级的PLCA内自然保护区的自然土地覆盖面积损失和生物多样性完整性与未受保护的控制点之间的差异来量化南非PLCA的有效性。PLCA中的点与未受保护的控制点相匹配，以测试以下预测：如果PLCA提供有效的保护，与暴露于类似条件的未受保护的对照相比，其范围内自然土地覆盖和生物多样性完整性的损失将大大降低。因此，评估了自然土地覆盖丧失对生物多样性完整性的后果，从而推动了量化有效性的标准方法。在1990年至2013年之间，PLCA的自然土地覆盖率（3％）和生物多样性完整性（2％）的损失要比相应的未保护地区（分别为6％和4％）少得多。在PLCA内失去的自然土地覆盖物中，大多数被转化为耕地。与其他土地用途（例如矿山）相比，农场可以提供更多的物种，一个可能的解释是，为什么生物多样性完整的损失少于自然土地覆盖的损失。与预测的模式相反，有效性并未随保护水平的提高而增加；没有受到法律保护的非正式PLCA具有与严格保护的PLCA相当的自然土地覆盖率和生物多样性完好性，其中损失最多的是受到中等保护的PLCA。这项研究提供了第一个全国性的证据，表明PLCA可以成为保护自然土地覆盖和生物多样性完整的有效机制，考虑到当前有关其长期生物多样性保护能力的讨论，这是高度相关的。没有受到法律保护的非正式PLCA具有与严格保护的PLCA相当的自然土地覆盖率和生物多样性完好性，其中损失最多的是受到中等保护的PLCA。这项研究提供了第一个全国性的证据，表明PLCA可以成为保护自然土地覆盖和生物多样性完整的有效机制，考虑到当前有关其长期生物多样性保护能力的讨论，这是高度相关的。没有受到法律保护的非正式PLCA具有与严格保护的PLCA相当的自然土地覆盖率和生物多样性完好性，其中损失最多的是受到中等保护的PLCA。这项研究提供了第一个全国性的证据，表明PLCA可以成为保护自然土地覆盖和生物多样性完整的有效机制，考虑到当前有关其长期生物多样性保护能力的讨论，这是高度相关的。