Discounting is standard in economics to consider time preferences of people and account for future market changes. However, so far discounting has mainly been applied to monetary flows and ignored for many ecosystem services. In multi-objective optimization, selectively disregarding time preference for some non-monetary services create bias. Here we study how discounting a range of ecosystem service indicators influences a public planner's optimal land allocation. We used a robust multi-objective optimization approach to model a mixed forestry-avocado farm portfolio in South Africa. The objectives for optimization were the provisioning of various ecosystem services and disservices represented by four indicators: net present value, payback period, carbon sequestration, and fertilizer use. To account for time preferences concerning indicator flows, we applied specific discount rates to each ecosystem service indicator, depending on its character (non-monetary or monetary indicators). We demonstrate that discounting reduces the standard deviations of the discounted sum of the indicators, which leads to less diversified land-use portfolios. To account for discount rate uncertainty, we introduced three indicator sets simultaneously, each using a different discount rate, which was off setting the effect of decreasing diversification.

贴现是经济学中的标准，用于考虑人们的时间偏好并考虑未来的市场变化。然而，到目前为止，贴现主要应用于货币流动，而在许多生态系统服务中被忽略了。在多目标优化中，选择性地忽略某些非货币服务的时间偏好会产生偏差。在这里，我们研究了贴现一系列生态系统服务指标如何影响公共规划者的最佳土地分配。我们使用稳健的多目标优化方法来模拟南非的混合林业-鳄梨农场组合。优化的目标是提供由四个指标表示的各种生态系统服务和损害：净现值、投资回收期、碳固存和肥料使用。为了考虑指标流的时间偏好，我们根据其特征（非货币或货币指标）对每个生态系统服务指标应用了特定的贴现率。我们证明贴现降低了指标贴现总和的标准差，从而导致土地利用组合的多元化程度降低。考虑到贴现率的不确定性，我们同时引入了三组指标，每组使用不同的贴现率，这抵消了减少多元化的影响。