Indicator species

Indicator species – free agri-monitoring tools for your farm!

Indicator species are animals or plants whose presence provides particularly useful insights into the health and quality of your farmland.


For farmers, indicator species provide:

  • A practical, free monitoring tool!

Indicator species can signpost changes in the quality of your soil, water and other conditions that are important for crop growth and productivity. For example, many earthworms can indicate healthy soil, many docks can indicate soil compaction, while many frogs and newts in wetter areas can indicate good water quality!

  • An early warning system!

Indicator species are like the canary in the coal mine; they respond quickly to changes in the environment. If you know what your indicator species are telling you, you can catch environmental issues early on, saving time and resources in the long run.

Below are a few examples of what to look out for on your farm!


 1. Weeds: friend or foe?


Getting to know your docks could be a secret weapon in terms of understanding and improving the long-term health of your pasture. Docks grow in areas where soil health is poor. This is generally as a result of disturbance and compaction over time. Excessive fertilizer use will only encourage the growth of docks, while spot spraying will kill the docks but will also kill off other useful plants in your pasture. Removing docks by digging or pulling is not very effective and will lead to more soil disturbance, which will likely lead to ever more docks! So what to do with docks?!

Before waging all out war, it’s important to remember that docks have likely colonized your pasture because there is an underlying problem with the soil. Therefore, building soil health and fertility should naturally help to reduce docks – check out our resources on soil health to help you get started. Regular cutting and grazing (before docks go to seed) will also help to reduce docks over time. Finally, eliminating pesticides can allow the iridescent green dock beetle (also known as the mint beetle) to populate your pasture. The larvae of this beetle enjoy nothing more than shredding and munching on dock leaves through August and September!

It’s also worth considering the role that docks are actually playing in your pasture. That strong, deep tap root (ever tried to pull one up?!) is reaching below ground, breaking up areas of compacted soil and carrying important nutrients back up to the surface where they can be reached by the more shallow rooting grasses. When you reflect on this, docks are actually out there doing us farmers a favour – might be worth leaving the odd dock to do this heavy lifting for us?


Ragwort, (also known as buachalán or buachalán buidhe) is a native wildflower with bright yellow petals. Ragwort contains toxins that can cause liver poisoning in horses and other livestock. Usually, if there is plenty of other forage in the field, livestock will not eat ragwort. However, once it is preserved in hay or silage, cattle and horses will readily eat it. As such, it is considered a ‘noxious weed’ and great care must be taken to avoid making hay or silage that contains ragwort.

Just like other native plants, ragwort can give a helpful indication of the health of your soil. While it can take hold in a wide variety of soil types, ragwort grows best on lighter, free-draining soils, where fertility has been enhanced and heavy grazing pressure has left gaps in the sward. As such, the presence of ragwort in grassland indicates that the land has been managed intensively. Good grazing management will prevent the establishment of ragwort in pastures – next time you see a few yellow heads pop up, perhaps it’s a good reminder to consider how stocking rates and nutrient management plans can affect the long-term health of your pasture.

Ragwort can be pulled by hand (wear gloves though as the toxin can be absorbed through the skin) or cut before it goes to seed. If you are pulling or cutting, make sure the plants are removed from the field as animals are more likely to eat the dead material than the living plant. Spot spraying is not recommended as, again, the plant will become more palatable once dead and may then be eaten by livestock on the next rotation. For larger areas, ploughing can be an effective control method, although seed can still stay dormant in the soil for up to 20 years. Likewise, as individual ragwort plants do not all germinate at the same time, herbicides are not very effective. The best way to manage ragwort, therefore, is prevention – good grazing and nutrient management (i.e. not overdoing either!) will help to keep ragwort from taking control of your pasture.

Finally, while ragwort is much maligned, it’s an attractive native flower and beneficial to a wide range of insects, particularly the black and yellow stripped cinnabar moth caterpillar!


Thistles occur on almost all soil types but can often indicate clay soils that are nutrient rich, deep and have reasonable water retention.

Creeping thistles are perennials and spread by roots that ‘creep’ through the soil. Spear thistles are annuals/biennials and spread through seed. Within species rich grasslands, thistle control need not be about complete elimination, but rather about achieving a manageable balance. Prevention is better than cure – keep your soil covered and avoid overgrazing and poaching, both of which lead to gaps in the sward where thistles can gain a foothold. If you are overrun with thistles, a combined approach using good grazing practices and well-timed mechanical topping can help to reduce the burden over time.

While thistles are useful to the farmer in terms of indicating soil fertility, it’s important to remember that they are also useful to many species of wildlife; they provide an important nectar source for butterflies such as the meadow brown and an important source of seed for birds like the goldfinch, twite, linnet, siskin and redpoll.


Dandelions generally indicate that soil is compacted and may be low in calcium. Just like docks both indicate and help to address soil compaction, dandelions both indicate and help to address low soil calcium. Dandelions have long taproots that reach much into much deeper layers of soil than the roots of grasses. These tap roots then carry calcium and other nutrients back up to the nutrient depleted surface levels of the soil, improving soil health and doing the farmer a favour!


Nettles indicate nitrogen rich soils and often grow in the field boundaries of heavily fertilised fields. If this is the case on your farm, then your nettles may be indicating that some of your valuable nutrients are escaping past the fence line. Enriching the soils outside of our pastures is beneficial for nettles, but overall it reduces the diversity of plant life in field boundaries and hedgerows. If there are a lot of nettles on your farm, consider ways in which you could reduce the application of chemical fertilisers and mitigate against costly run-off from your pastures.

Of course nettles are by no means all bad – they also support a great diversity of insects and can make a tasty high-protein snack for some grazing livestock! If you have limited nettles on your farm, do consider allowing a few patches to grow wild, particularly in a sunny spot in the middle of a field, and watch how they attract butterflies in the summer!


Those green spears that shoot up out of wet grasslands may seem like just a weed, but they can also provide crucial insights into the health of your farm landscape. Rushes love wet, compacted and disturbed ground. As such, they can often indicate that the underlying soil has been too heavily grazed, poached or has been damaged or disturbed in another way, such as by farm machinery or flash flooding.

If you have rushes, it’s probably better to accept that you may always have a few rushes than attempting total annihilation! Perhaps give them a nod for indicating that your soil needs some attention and then move on to focussing on the real issue at hand – the quality and health of your soil. If you really need to tackle the rushes head on, then regular cutting can weaken the rushes over a few years, giving grasses the opportunity to successfully compete with them for light and nutrients. Some farmers have also had success with adding donkeys to their grazing rotation. Donkeys will eat rushes if there is little else to eat. However, equines can quickly overgraze an area too, so care must be taken in their management.

Finally, avoid using herbicides on rushes, particularly in wet areas. Many synthetic herbicides are water-soluble (e.g. MCPA, 2,4-D); as such it is almost impossible to ensure they do not end up in watercourses after application!

Next time you’re out and about, remember to read your weeds!


2. Insects

Insects don’t just pollinate our food crops, they also provide crucial clues as to the health of our environment. For example, the presence and diversity of aquatic insects such as mayflies, stoneflies and caddisflies can be used to assess the health of rivers, streams and lakes. These insects are particularly sensitive to water quality, so if they are thriving in water bodies on your farm, it’s a good sign that the water is clean and healthy. Likewise, if their populations are low, it could indicate water pollution or other environmental problems. Similarly, an abundance of moths, bees and butterflies is a good sign that the environment is healthy (and also that there is an army of winged insects waiting to pollinate your crops)!

If your farm is not buzzing and humming with life in summer, it’s worth thinking about how you can improve the health of your farm environment. Is it possible to reduce or eliminate pesticides? Are there areas of the farm that could be managed for wildlife? How clean and healthy are the waterways on your farm?

3. Birds

Birds are a pleasure to have around the farm all year round, but are particularly delightful in spring when their lively chorus coincides with lengthening days and warmer weather. However, birds provide more than just farmyard entertainment – they can also offer helpful hints as to the health of your farm environment! Because birds sit relatively close to the top of the food chain, their presence on your farm demonstrates that the species that they rely on to feed (e.g. insects or seeds) or breed (scrub, woodland, wetlands, rough grasslands) are also in good ecological condition.

As well as teaching us more about the kind of resources our farms are providing for wildlife, monitoring birds on our farms can help us to understand if we are moving in the right or wrong direction in terms of ecologically sustainable practices.

For example, if you remember hearing a lot more birdsong on the farm when you were a child than today, some of the more modern management practices on the farm may be making it increasingly difficult for birds to survive and thrive. If this is the case, then perhaps it’s worth considering adjusting your management practices to create more space for nature. If you’ve already made changes to your farming practices to enhance nature, then the return of deep, mellifluous and multi-levelled birdsong in spring will no doubt reassure you that you’re on the right track!

4. Mammals

Observing and considering what mammals are getting up to around your farm can offer valuable insights into the health of your ecosystem and allow you to make more informed decisions about land management and conservation.

For example, the presence of foxes and badgers can be used as an indicator of the abundance of smaller mammals, such as rodents, which are an important food source for both these mammals and for owls and other raptors. The presence of otters in your waterways can indicate that these habitats are clean and that they support a good supply of fish, while the presence of red squirrels and pine martins in your woodland can suggest that this habitat is healthy and diverse.

The presence of some mammals can also indicate when it is time to take action to protect existing habitats on your farm. For example, the ever-expanding population of non-native deer in Ireland (sika deer, fallow deer and Reeve’s muntjac deer) is preventing many woodlands from naturally regenerating. If you regularly spot these species on your land, you might consider fencing off some habitats to prevent them from being over-browsed by hungry deer!

5. Lichens

Those crusty, colourful bunches growing on rocks and trees may seem like just another of nature’s weird and wonderful adornments, but they’re also amazing indicator species, giving farmers a sneak peek into the health of their environment.

Lichens are particularly sensitive to air pollution: if your trees, rocks and walls are bedecked with lichen then you’re likely breathing in clean and healthy air!

6. Fungi

Spotted any mushrooms recently? A diverse and abundant fungal community is a great sign of soil health on a farm.

Did you know that any mushrooms (fungi) that we observe around the farm are only small parts of much larger organisms? The mushroom is the fruiting body of the fungus. Underground, the fungus comprises a complex network called a mycelium. A mycelium is made up of tiny hair-like structures called hyphae. These hyphae can stretch through the soil for many metres: in fact, a single cubic inch of soil can contain eight miles of entangled mycelia! These fungal hyphae are always busy below ground, binding soil, improving drainage, breaking down organic matter and returning nutrients to the soil. Many fungi also produce antifreezing agents, which have evolved to protect their mycelia during cold spells. These agents are the farmer’s friend – protecting the roots of grasses and other plants when temperatures drop below zero.

Fungi can also form mutually beneficial relationships with the roots of both wild and cultivated plants. The hyphae of mycorrhizal fungi carry nutrients, water and chemical messages to and from plant roots. In turn, plants provide the hyphae with plant-secreted sugars. Plants with healthy mycorrhizal fungal partners benefit from increased availability of soil nutrients and moisture, as well as greater resistance to disease. These vast interconnected messaging and trading systems have been dubbed nature’s internet or the ‘wood-wide web’!

The best time for spotting mushrooms around the farm is from July to November. However, in healthy soils they can pop up here and there all year round. If you haven’t spotted many mushrooms around the farm recently, it might be worth looking at your soil management regime. Tillage, fungicides and chemical fertilisers break up fungal hyphae and inhibit the growth of healthy soil-enhancing mycelia. Reducing chemical inputs, minimising tillage and incorporating organic matter into the soil can all help to promote a healthy population of mycorrhizal fungi.

7. Earthworms

Earthworms play a crucial role in breaking down organic matter and improving soil structure; if they’re thriving in your soil it’s a great sign that your soil is healthy.

Depending on the soil type, healthy soil will contain 50-250 earthworms per square meter. Higher populations of earthworm usually indicate fertile, well-drained soils with reasonable water retention and organic matter. Likewise, low earthworm populations can indicate soil compaction, poor drainage, or low organic matter, all of which impact soil health and can reduce soil yields.

Don’t be afraid to get your hands dirty and dig a few holes to investigate your soil for earthworms! If you’re ploughing, the crows and gulls will also indicate to you whether you have a healthy population of earthworms; a cloud of birds following the plough is usually a good sign of a healthy earthworm population!

If you don’t have many earthworms in your soil, then you might consider taking some steps to start building back soil health and fertility – check out our resources on soil health to help you get started.


Next time you’re out and about, see if you can spot any useful indicator species that are providing clues about the health and quality of your farm environment!

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