The pollination tragedy

Abstract

The creation of floral resources for pollinators, such as flower strips, is seen as a relevant and needed intervention but comes with both cost and an opportunity for farmers. It may be worth it if, for example, pollinators are attracted to pollinator-dependent crops and deliver crop pollination. Unfortunately, since pollinators are mobile organisms, the spatial distribution of crop pollination resulting from a flower-strip addition is still unclear, making it difficult to understand who is benefiting from the resource addition. This exposes such ecosystem service to the “tragedy of ecosystem services”, that is the under provision of ecosystem services from privately owned land due to the difficulty of landowners to internalise benefits on their properties. Here, a spatially explicit process-based pollinator model was used to spatially locate the benefit generated by a flower-strip addition, with the aim to enhance pollination of oil seed rape specific fields. Results show that on average 30% of the extra crop pollination generated by the FS addition is lost to neighbouring oil seed rape fields. This is when only looking at benefits to oil seed rape in the landscape. Losses varied across areas with different agriculture intensity, with less intensively cultivated areas losing smaller shares of crop pollination to the neighbouring fields compared to the more intensively cultivated areas. At the same time, when looking at all fields and crops in a landscape, on average 80% of crop pollination are lost to the neighbouring lands. In such a case, the targeted fields in less intensively cultivated areas internalised smaller amounts of crop pollination compared to the ones in more intensively cultivated areas. Hence, there are clear indications that pollination is experiencing a tragedy of ecosystem service, with farmers losing shares of FS benefit to their neighbours. These results, in accordance with multiple previous works, show once more the need of a collaboration at the landscape level to reach an optimum level of pollination delivery to crops. Further studies may help to better quantify the monetary support needed by farmers to guarantee higher yields, possibly leading to a fairer and more equal share of management costs between the farmers and the public.

Popular Abstract

Bees and Flower strips

Did you know that bees require flowers and nesting sites to sustain themselves in the landscape? Just like us, they need food and a nice place where to nest. Unfortunately, with agriculture intensification, these resources have decreased. Today, scientist suggested that creating flower strips in agricultural landscapes can help bees. These flower strips are simply patches of flowers sown on part of the fields. They are believed to help the bees because they represent a floral resource, that is simply the food that bees feed on. For a farmer, sowing a flower strip is, first of all, a cost. He is in fact sacrificing a piece of field to support and attract pollinators to his land. So, he is not growing any crop on that specific piece of field, causing a direct loss of money to himself. On the other hand, this measure may represent an opportunity for the farmer if the bees pollinate his crops. There are in fact some crops that benefit from being pollinated by insects, leading to higher and more quality yields! This is the case of oil seed rape, a well-known crop in south of Sweden. In spring, oil seed rape fields become all yellow because of the many small flowers that this crop produces. These flowers are believed to support the bees while in bloom since they provide food for them. So, attracting the bees to these crops can both help the bees and the farmer!

Going back to the flower strips, it is easy to understand that this measure becomes worth it only if the extra yield can compensate the crop loss caused by the flower strip itself. Hence, demonstrating that the farmer does indeed attract bees to his fields is crucial. In fact, on the long run, it has been suggested that these measures (the flower strips or any measure to help bees that can cause a loss of money for the farmer) may be underprovided by the farmers because they have difficulty to converge the pollinators on their lands. If you think of it from a bee perspective, they do not really care about who is owning the different fields in the landscape, they are just looking for food and a nice place to nest. So, they may end up on the neighbours’ fields, increasing the yield of someone that has not done the effort, and taken the cost of sowing a flower strip. Since the bees are organism that do move in the landscape, it is easy to understand that it is quite difficult to convey them only on a specific field or farm.

In my study, I used computer simulations to investigate what happens when you add a flower strip to a field, especially in terms of where the bees tend to go in search of resources. My results show that on average, the land of the famer that added the flower strip received on average 40% of the visitations, while neighbouring fields received the remaining 60% of visitations. At the same time, when only focusing on the single field that received the flower strip, my results show that it received on average only 20% of the visitations. I also checked the visitations to the oil seed rape fields of the farmer that added the flower strip compared to the oil seed rape fields of the neighbours. In this case, the fields of the farmer that took action to add resources for the bees received, on average 77% of the visitations.

With this study I generated a new piece of knowledge about how difficult it is to convey the bees only on the fields and land of one single farmer, confirming that this may cause, on the long run, a diminishment of farmers that add flower strips to their lands. In fact, the bees may not spend enough time on the fields of the farmer to actually make the flower strips an implementation that is worth it. Considering how important bees are for all of us, this is a very bad news! But, before we start worrying, luckily studies from the past showed that if there is collaboration between farmers, and many add flower strips to the fields, then the problem is solved! In fact, the bees would finally have lots of food for themselves. This means that they would increase in numbers and even spread in the agricultural areas. This would finally allow to pollinate the crops of all farmers, compensating for the money loss caused by the flower strips. Collaboration is of course not easy to obtain, but it is still a solution! For example, it may require that either all the farmers add a flower strip or maybe that the ones adding it receive an economic compensation that pays for the added flower strip. We must not forget that we need to conserve these resources for the bees in the landscape. But, at the same time, we also must remember that we cannot expect farmers to pay for them, if a direct farmer-benefit is not generated. So, solutions for sustainable pollination exist, but more knowledge is needed to help the bees and other pollinators to persist in the agricultural areas.

Master project in Conservation Biology, 45 credits, 2022
Department of Biology, Lund University.
Supervisors: Henrik Smith, Peter Olsson
Centre for Environmental and Climate Change

• author: Vezzani, Liam
• supervisor: Peter Olsson; Henrik Smith
• organization: Degree Projects in Biology
• course: BION02 20221
• year: 2022
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9113485
• date added to LUP: 2023-04-14 14:29:32
• date last changed: 2023-04-14 14:29:32