Measuring Farmland Biodiversity

Dr Neus Rodriguez-Gasol explains how farms can be surveyed for biodiversity and provides details on the surveying techniques used by the Protecting Farmland Pollinators EIP Survey Team.

 

 

Nowadays it is well known that the world is experiencing a severe biodiversity decline with many species either disappearing or significantly reducing their distribution and population numbers.

Multiple factors have contributed to this global biodiversity decline, such as land and water pollution, over-intensive farming, and habitat destruction. With about 40% of land in the European Union under agricultural use (about 70% in Ireland) there is much that can be done in agricultural landscapes to help biodiversity. Therefore, farmers are in a great position to protect or even promote biodiversity within their management decisions. However, they need sufficient knowledge to make informed decisions and here is where expert advisors can help.

Since it is difficult to measure biodiversity as a whole, different survey methods and techniques depend on biodiversity indicators which provide information to express the size, extent or degree of biodiversity (e.g. presence of semi-natural habitats, number of different species, availability of food and nesting resources).

 

Species abundance, richness and diversity are common measures to help capture part of the complexity of biodiversity.

  • Species abundance refers to the number of individuals of each species in an area. Relative species abundance is how common a species is relative to the other species in a defined location.
  • Species richness refers to the number of species in an area.
  • Species diversity considers both, the number of species (species richness) and the abundance of each species (relative abundance) present in an area. So it takes into account not only how many species are present but also how the numbers of each species are distributed.

 

There are several sampling methods and techniques available for measuring biodiversity on farmland which will differ depending on the organism we want to study e.g. transect walks, pitfall traps, light traps, to name a few.

 

Figure 1. Pitfall traps are used to capture species that can be found in the ground and soil litter such as spiders, beetles or amphibians (the size of the pitfall trap will differ depending on the group we want to collect).

 

Figure 2. Light traps are illuminated traps used for attracting and catching nocturnal flying insects like moths.

 

Each sampling method has its own limitations, so using a combination of these methods is the most effective approach for community studies e.g. comparing biodiversity on different farm types (beef, dairy, mixed and tillage).

 

Pollinators are important to farmers, to our economy and to the health of our environment. The Protecting Farmland Pollinators EIP Project aims to help farmers identify and implement small actions to help maintain pollinator (wild bees and hoverflies) populations and other biodiversity that will allow biodiversity to co-exist within a productive farming system. For that purpose, the project will develop and test a whole-farm pollinator scoring system that can be easily calculated, easily understood and easily improved (and in line with the All-Ireland Pollinator Plans Farmland Guidelines).

 

In order to identify what management practices on Irish Farmland benefit pollinators, diverse survey techniques will be used on the farms in order to understand the existing biodiversity on each farm and link it with the pollinator score card results. The surveys will mainly focus on monitoring pollinators and plants.

 

1. Pollinator monitoring

In order to monitor pollinator diversity and abundance three types of surveys will be conducted in the farms: visual transect walks, pan trapping and malaise trapping.

 

1.1 Visual transects walks (Pollard walks)

Visual transect walks involves the surveyor walking at slow speed and focusing on any potentially attractive resource patches within 2.5m of the surveyor at each site and 5m from the ground. Each walk will last about 30 minutes and all pollinators including their activity (flying or visiting a flower) will be recorded. The visited flowers will also be recorded. The pollinators that cannot be identified in the field will be captured and preserved for later identification in the laboratory. Transect walks will only be performed under good weather conditions (warm sunny days).

 

Figure 3. Visual transect.

 

These transects will be carried out in the flower-rich fields (e.g. wildflower meadows, flower-rich pastures, cover crops, herbal leys) and the hedgerows. In the first case the walks will be in a W shape, while in the second they will be conducted along the hedgerow.

 

1.2 Pan traps

Pan traps will be set up in the flower rich fields. These traps are used to attract and capture small flower visiting insects present in the vicinity, nonetheless they can capture other non-pollinating insects. All you need for a pan trap is a small coloured pan or bowl filled with soapy water. Different colours are used to attract different insects, yellow, blue and white are the most common colours used. Usually, clusters of 3 pan traps (one of each colour) are placed in the field at vegetation height, filled with water and a drop of dishwasher soap. The soap is used to break the surface tension of the water, so the insects will fall through.

Pan traps will be set up for 24 hours under good weather conditions (sunny warm days).

 

Figure 4. Left: Pan trap setting in a flower rich field. Right: Detail of insects captured by pan trapping

 

1.3 Malaise traps

Malaise traps are based upon the observation that most flying insects hitting an obstacle respond by flying or crawling upward. These traps consist of a mesh tent-like structure with a collection head situated at the highest point. When it is activated, the trap has only an open side, so when the insects fly into the tent wall they migrate upwards where they are collected in a bottle or container. The collecting bottle will contain ethanol which will preserve the specimens for later identification in the laboratory.

Malaise traps are particularly suited for the study of flying insects (such as bees, wasps and flies) and are a way of augmenting catch and collecting rare or ephemeral representatives. These will be used to evaluate the maximum biodiversity per farm in terms of flying insects (biomass and abundance). Traps will be located near the same hedgerows in which the transect walks will be done.

 

Figure 5. Left: Malaise trap setting. Right: Malaise trap set up.

 

1.4 Bee nesting sites

Suitable nesting sites are a known limiting factor for some of our wild bees in Ireland, for this reason the abundance and richness of the different species nesting in the farms will also be assessed. Two types of nesting sites will be monitored: cavity bee nesting sites and mining bee nesting sites.

 

Figure 6. Left: mining bee entering into its nest. Right: cavity bee nest.

 

2. Plant monitoring

The plant species survey will give information about plant diversity, richness, and abundance, as well as the available resources for pollinators in each farm. As with the pollinator surveys and in accordance to the Protecting Farmland Pollinators score card, the plant assessments will also be conducted in the hedgerows and the flower rich fields. The same transect walks to survey pollinators will be used. In these transects, quadrats will be used to assess plant diversity and flower abundance.

 

Figure 7. Quadrat placed for plant assessment in a flower rich field (left) and hedgerow (right).

 

Hedgerow structure will also be examined, characteristics such as, time since cut, hedge width and height, percentage of gaps and associated linear features (e.g. water streams) will be recorded.

Finally, pollinator friendly tree species will also be recorded on each farm in order to allow further determination of the potential bee feeding and nesting resources. For a list of pollinator friendly trees see https://pollinators.ie/wordpress/wp-content/uploads/2018/04/Planting-Code-2018-WEB.pdf.

All the mentioned surveys will help develop and check the EIP Project scoring systems. These will help farmers understand how pollinator friendly their farms are and what simple low-cost actions can be taken to improve pollinator conservation without any negative impacts on productivity. In taking action to protect pollinators we start a chain reaction that has positive benefits for the general health of our environment, and the well-being of future generations. For more information about the EIP project visit https://www.biodiversityireland.ie/farmland.

 

Neus Rodriguez-Gasol is employed as a member of the Ecological Survey Team for the Protecting Farmland Pollinators project with the National Biodiversity Data Centre. Neus conducted her PhD on “Habitat management in Mediterranean fruit orchards to foster pollinator and natural enemy communities” at the Institute of Agrifood Research and Technology (IRTA) and the University of Lleida.