Estimating landscape structure efects on pollination for management of agricultural landscapes

Background:The growing human population around the world is creating an increased demand for food.In agricultural landscapes,forests are cleared and turned into agricultural land to produce more food.Increasing the productivity of agricultural land per unit area may prevent extreme forest degradation.Since many agricultural products are dependent on pollinators,it is possible to increase crop production by increasing the pollination rate in the agricultural landscapes.Pollinators are highly dependent on forest patches in agricultural landscapes.Therefore,by creating new forest patches around agricultural felds,we can increase the pollination rate,and thus the crop production.In this regard,estimating the efects of diferent scenarios of forest fragmentation helps us to fnd an optimized pattern of forest patches for increasing pollination in an agricultural landscape.Methods:To investigate the efect of diferent forest fragmentation scenarios on pollination,we used simulated agricultural landscapes,including diferent forest proportions and degrees of fragmentation.Using landscape metrics,we estimated the relationship between pollination and landscape structure for each landscape.Results:Our results showed that for increasing pollination,two signifcant factors should be considered:habitat amount and capacity of small patches to supply pollination.We found that when the capacity of small patches in supplying pollination was low,fragmented patterns of forest patches decreased pollination.With increasing capacity,landscapes with a high degree of forest fragmentation showed the highest levels of pollination.There was an exception for habitat amounts(the proportion of forest patches)less than 0.1 of the entire landscape where increasing edge density,aggregation,and the number of forest patches resulted in increasing pollination in all scenarios.Conclusion:This study encourages agriculturists and landscape planners to focus on increasing crop production per unit area by pollinators because it leads to biodiversity conservation and reduces socio-economic costs of land-use changes.We also suggest that to increase pollination in agricultural landscapes by creating new forest patches,special attention should be paid to the capacity of patches in supporting pollinators.

Using the Lonsdorf model for estimating habitat loss and fragmentation effects on pollination service

One of the most important issues related to landscape ecology and ecosystem services is finding the pattern of habitat patches that offers the highest pollination in agricultural landscapes.In this regard,two processes of habitat loss and fragmentation strongly affect the relationship between pollination and the pattern of habitat patches.In the present study,we aimed to examine the effects of habitat loss and fragmentation on pollination separately.For this purpose,first,we generated different simulated agricultural landscapes,including two habitats of forest and agriculture.Then,according to the Lonsdorf model,we estimated the potential of the simulated landscapes in providing pollination in different scenarios.Finally,using statistical models,we estimated the effects of habitat loss and fragmentation on pollination at the landscape and farm levels.Our results showed that the effects of habitat loss and fragmentation on pollination were completely different at the landscape and farm levels.At the landscape level,fragmentation negatively affected pollination,but at the farm level,the maximum pollination rate was observed in the landscapes with a high degree of fragmentation.Regarding the habitat loss effects,our results showed that pollination decreased linearly at the landscape level as habitat amount decreased,but at the farm level,it decreased exponentially.The present study considered the level of analysis(i.e.,landscape and farm levels)as a critical factor affecting pollination changes caused by fragmentation.We showed that using the Lonsdorf model could lead to confusing results for the landscape ecologists and alert farmers who want to reduce the adverse effects of fragmentation on their products by creating new forest patches.Therefore,agriculturalists and landscape ecologists should consider that the pollination rate at the landscape and farm levels is completely different according to the model and provide contradictory results about the process of habitat loss effects on pollination.