The cooling effect of greenery

Extreme cold or heat, rain, gusts of wind, severe thunderstorms, snow, ice, or long periods of drought… You’ve probably already noticed it yourself, we are increasingly experiencing extreme weather conditions. The societal challenge of keeping cities livable means that we need to adapt our cities to the changing climate. One way to do this is through greenery. Greenery is essential for a climate-resilient and sustainable urban environment. Greenery provides cooling, reduces waterlogging, and increases infiltration capacity, which also helps combat drought. But how do we create green cities? And how do we ensure that the costs of green management don’t skyrocket?

Author: Malon Gerrits

Evaporation processes have a cooling effect on air and surface temperatures. In a natural environment, trees provide shade, lower surface temperatures, and air temperatures. However, large percentages of buildings and other paved surfaces result in lower evaporation.

Material properties related to the reflective and heat-absorbing capacity of sunlight affect surface temperature and, therefore, the air temperature in the city. The reflective capacity of sunlight is called albedo.

Hard surfaces and building materials in urban areas generally have a lower albedo than vegetated surfaces. The materials in urban areas reflect less and absorb more sunlight, leading to higher surface and air temperatures. This also means more smog formation. Warm air carries pollutants and dust particles to higher atmospheric layers, creating a smog layer. Cooler air from outside the city is warmed up at the urban fringe and does not penetrate into the city center.

The most effective measure to limit surface temperatures is to reduce the percentage of paved surfaces.

10 air conditioners cool as much as 1 tree

Trees are natural problem solvers. Trees and greenery have a cooling effect on the urban climate because they reduce solar radiation on the Earth’s surface through shading and absorb heat through the evaporation of moisture from leaves.

Research even shows that in summer (depending on the tree species), only 10% to 30% of sunlight reaches the ground in the shade of a tree. Various studies in America have shown that walls in the shade of trees are on average 20°C cooler. The research “The Heat-Resilient City” by the Amsterdam University of Applied Sciences describes that a 10% increase in greenery leads to half a degree less heat in the city.

Reduced peak runoff during rainfall

Greenery is not only beneficial for limiting warming but also offers advantages for water management. Greenery reduces peak runoff during rainfall. Instead of flowing directly into the sewer, the water is first stored by leaves or branches. Only when these become saturated does the water flow into the ground. As a result, a portion of the rainfall reaches the ground with a delay, and another portion evaporates. This reduces the simultaneous discharge of rainfall and reduces waterlogging.

The evaporation of water by greenery, the ground beneath it, and its surroundings contributes to reducing heat stress by achieving a 2°C to 5°C lower air temperature in the immediate vicinity. Additionally, it enhances biodiversity and quality of life potentials.

Leaf canopies of trees or pergolas above parking lots, squares, schoolyards, and playgrounds help keep the city cooler. They also reduce airborne dust and other pollutants, improve rainwater retention, and enhance overall quality of life. Unfortunately, greenery in and around cities is still under significant pressure. More trees are being cut down than planted, and there is an increasing trend of urban green spaces being built upon and paved over.

Slowly, this is starting to change, and more and more people are realizing the benefits of greenery for a city. Urban planners are recognizing the importance of investing in sustainable development.

Vital importance

Trees are therefore vital, but they need to be healthy and mature.

Greenery also has a water demand. During times of drought and water scarcity, greenery can exacerbate the problem. Attention is therefore important; by the time you can see the problem on the tree, it is often already too late. If you give the tree too much water, it will receive little to no oxygen at the roots. This not only makes the tree “lazy” by preventing root development compared to the crown, but in the worst case scenario, the tree can die. You can prevent this by planting the right trees in the right places, storing and conserving rainwater for dry periods, and through monitoring. Monitoring is simply necessary to allow greenery to grow in less natural areas such as city centers, viaducts, or rooftops.

Cost-effective management

Watering is customized and dependent on the conditions. It is not possible to provide a fixed amount and frequency. This makes monitoring water levels even more important. That is why since 2017, we have been helping green space managers, municipalities, landscapers, provinces, growers, and water boards work smarter and more efficiently. We achieve this by combining knowledge about trees and plants with the “Internet of Nature.”

ConnectedGreen is a smart system for remote monitoring of green projects, trees, beds, containers, lawns, and roof and wall greenery. The system consists of wireless sensors, a smart cloud environment, and user-friendly apps for both clients and contractors. This fosters better collaboration, and the measurement data is valuable for use in asset management systems and work planning (data-driven work). At the same time, it leads to significant cost savings in replanting, watering, and project visits.

Over 1500 of our wireless sensors have already been installed in projects throughout the Netherlands and Belgium.

Significant savings

In the municipality of Veldhoven, around 300 trees were knocked down by storm damage in 2019. The 70 trees that were replanted are now being cared for based on the data from the sensors. A total of 840 new trees have been planted in the municipality of Veldhoven. “The investment in the sensors and the accompanying subscription pays for itself quickly,” says green advisor Ron Berben. “After three months, I calculated the difference. If we had cared for all 840 trees based on the moisture sensors, we would have saved €20,000 in water, labor, and material costs over three months. I’m genuinely surprised. You don’t waste water, but you also don’t give too little, so the tree is optimally cared for. And there’s no need for extra trips to check the status of the tree and the soil. That’s an additional internal saving that isn’t included in the amount. The execution can also be monitored. The moisture sensors spike when water is given.”

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In the Netherlands, we had a problem that no one saw coming, such as drought, but due to climate change, we have to face it. Our rainy country is transforming into a land that must consider heat stress. In parts of Twente and Salland, the Vechtstromen water authority has even imposed a groundwater extraction ban for some of these areas. But how can a wet country like the Netherlands face such an issue, and should other regions take similar measures?

Author: Isabelle Horneman

Water is so abundant in the Netherlands that it is difficult for us to imagine a water shortage. However, it has become an increasingly significant problem in recent years. This is due to climate change, which leads to rising temperatures and increased evaporation of water. When more water evaporates than rainfall, we experience drought. Additionally, global warming in the Netherlands and surrounding areas also leads to a slight increase in precipitation. However, the catch is that climate change also causes much stronger variations. Rain showers become heavier, resulting in more instances of waterlogging. On the other hand, heatwaves occur more frequently, last longer, and become even hotter. Dry periods can also be prolonged and cause more disruptions.

Consequences of Drought

Drought has consequences for agriculture, nature, shipping, homes, and our drinking water. The Dutch water management system is primarily designed to drain large quantities of water, preventing fields from flooding, but due to drought, we now need to focus on better water retention. Farmers cannot continuously irrigate their fields with water from ditches, rivers, and canals, as it would deplete the water levels too much. This, in turn, creates problems for shipping, with ships being unable to navigate rivers like the Maas. These rivers also supply a significant amount of drinking water, so there can be implications for the water coming out of your tap. As a result of drought, the ground in the Netherlands is subsiding at a faster rate. Land subsidence is a well-known and problematic process in the Netherlands, where the ground level sinks in relation to a fixed reference point. This is caused by increased water extraction and the drying and compression of clay and peat soils during warm periods. Consequently, we are seeing more instances of shifting dikes and sinking houses and roads. Trees, plants, and animals also suffer greatly from drought as they struggle to access water and food. In summary, water is a vital resource in our country, so our focus should be on water retention.

Drought in the Netherlands

Precipitation is not evenly distributed throughout the Netherlands, although the differences are not significant. The driest areas are along the eastern border, in the eastern parts of Brabant, and especially in the central region of Limburg. Here, the average annual rainfall is around 750 mm, while the wettest regions receive approximately 950 mm of rainfall. As long as water flows into the Netherlands through rivers like the Rhine, the coastal provinces will never become truly dry. In the northwestern half of the country, the groundwater level is much higher than in the east and south. Large parts of provinces like South and North Holland would be submerged if we were to stop pumping water away. However, prolonged drought can cause problems in these areas, such as increased salinity of the groundwater. In the eastern and southern parts of the Netherlands, the situation is different. Especially in the higher sandy areas of provinces such as Brabant, Limburg, Gelderland, and Overijssel, the groundwater is often more than a meter deep and, in some places, even more than two meters deep. After a dry year, the groundwater level can be half a meter lower than usual, and this cannot be easily restored with a few wet days.


In Twente and Salland, during the dry summers from 2018, 2019, and 2020, it became evident that irreversible damage was being done to nature due to a lack of rainfall. With the risk of rainfall deficits exceeding 250 millimeters in that area, a groundwater extraction ban is now in effect in a portion of the management area south of the Overijsselse Vecht. This ban applies to the extraction of groundwater for irrigation and watering in vulnerable, groundwater-dependent nature reserves and within a 200-meter radius around these areas. The ban is in place because there is no significant rainfall expected in the foreseeable future. It is also crucial for maintaining water quality in the region. Insufficient rainfall and heat can lead to deteriorating water quality, which increases the risk of fish mortality due to oxygen depletion, the growth of blue-green algae, and botulism.

Increasing Greenery

Fortunately, more and more people realize that action must be taken against rising temperatures and changing weather conditions. But what can we do to mitigate these climate changes? Well, the answer is simpler than you might expect: more urban greenery! Green spaces in cities can play a crucial role in climate adaptation. They have a cooling effect, reduce waterlogging, and enhance moisture retention. However, greenery also requires water. During times of drought and water scarcity, green spaces can contribute to the problem. This can be prevented by selecting suitable locations for greenery and properly maintaining and caring for it. This is where ConnectedGreen comes in handy. Maintaining the appropriate soil moisture level is essential for the health of trees and plants. By monitoring it with ConnectedGreen’s sensors, you can work more efficiently, save water, and better preserve the well-being of trees and plants.

The greening of cities is becoming increasingly important and indispensable. Greening of cities is therefore on the agenda of many governments. However, the changing climate makes the management of this difficult. The municipality of Oldenzaal also found this out. Because what if you could determine the timing and routes of your irrigation based on the actual measured moisture content in the soil? They came to us with that question. Subsequently, a pilot project was started and our monitoring platform was integrated with Obsurv, the municipality’s management system.

Author: Isabelle Horneman

Managing green spaces

The greening of cities is becoming increasingly important and indispensable. Greening of cities is therefore on the agenda of many governments. However, the changing climate makes the management of this difficult. The municipality of Oldenzaal also found this out. Because what if you could determine the timing and routes of your irrigation based on the actual measured moisture content in the soil? They came to us with that question. Subsequently, a pilot project was started and our monitoring platform was integrated with Obsurv, the municipality’s management system.

Managing green spaces

It is difficult to determine when to water your green projects. When should you water? Should you water immediately or can it wait a little longer? A constant doubt that occurred in Oldenzaal. And rightfully so; you don’t want to provide too little water, but of course, not too much either. The use of sensors is therefore a perfect solution. By monitoring your green projects, you can reduce loss and irrigation and plan efficient routes, which also helps save costs.

Integration with an existing system

In addition to measuring soil moisture levels, ConnectedGreen’s platform can also be integrated with existing systems. This way, there is no need for drastic changes to be made within the existing management systems. However, before the integration with other management systems is realized, it is important to establish understanding and bring together data and application expertise with the experience and location knowledge of your project managers. Once that is the case, you can start integrating sensor data into your workflow. With the help of an open integration, for example, we were able to connect with the municipality of Oldenzaal so that our data was visible in their own management system.

The municipality of The Hague is an example of a customer who has been working with ConnectedGreen’s platform for a longer period of time. During the drought of the past summer, they frequently noticed that certain trees were already in the red while those trees were scheduled for watering later. Based on that information, they were able to adjust their routes on a daily basis and provide water to those trees in advance to prevent damage. This is a great example of the value that working with sensors brings. Especially considering the future and all the climate changes yet to come, it is important to be prepared for them.

Pilot phase

If you are also facing certain issues and are considering working with sensors in your green projects, you can always contact one of our colleagues at ConnectedGreen. Alternatively, you can request a whitepaper.


Infilling; for many, it may be a term that raises questions, but in the green sector, it’s quite normal. The jargon of this industry actually has a simpler meaning than you might think, so for those who have no idea what the term “infilling” means, we’d be happy to explain. Infilling is the replacement of plant material that has failed to establish or has been damaged after planting. Curious about what causes the loss of these new plantings and trees, and how ConnectedGreen can help prevent it? Keep reading to find out.

Author: Isabelle Horneman
Inboet case Ter Riele B.V.

Why do plants wilt?

After the implementation of new green projects, it is possible that they do not thrive well. There are various reasons why new plantings may not survive in these cases. Common causes of tree and plant mortality include:

  • Animals and pests that feed on the greenery
  • Damage from extreme weather such as frost or storms
  • Fluctuating groundwater levels
  • Vandalism
  • Drought

When searching for the cause, it is helpful to consider which of the above situations have occurred. The orientation of the trees or plants with respect to sunlight or shade can also have an impact, as well as factors such as the rate of green growth and whether the vegetation has the necessary space. Additionally, obtaining sufficient water is obviously an important factor in the establishment of new green projects, but with today’s climate change, it is uncertain whether plants receive too much or too little water. Plants can dry out during prolonged dry and hot periods, but excessive rain can lead to insufficient oxygen supply to the roots, resulting in the loss of greenery. However, imagine if you could determine the timing and routes of water supply based on the actual measured soil moisture levels. That’s something where ConnectedGreen can provide valuable assistance.

Ter Riele prevents loss of planting

Partner of ConnectedGreen, landscaping and green maintenance company Ter Riele B.V., is a good example of a company that wanted to reduce the chance of plant loss. One of the reasons for this was the dry years of 2018 and 2019. They wanted to manage the water supply. During those dry periods, they used to provide a lot of water, but they could never really verify if the correct amount of water was being given. Additionally, they operated on various types of soil, such as dry sandy soil or wet clay. By monitoring remotely, they could work more targeted and efficiently manage water, significantly reducing plant loss.

Landscapers can provide better replacement guarantees

Despite careful cultivation, it may happen that a plant or tree does not thrive in the chosen location. If a particular plant or tree does not perform well in a specific location, it may fail to establish. This is known as replacement.

Proper watering is crucial for the initial establishment of trees after planting. At the same time, it is important to prevent the tree from becoming dependent on watering. To provide the client with assurance that the planting will not fail, the contractor can offer a replacement guarantee. The client can also “demand” a replacement guarantee from the contractor. This often occurs through a bidding process and a multi-year framework agreement. To minimize the risk of replacement, monitoring is highly recommended.

ConnectedGreen helps prevent replacement

At ConnectedGreen, we have a good understanding of what replacement entails. Additionally, we are aware of how challenging it can be to combat this issue in today’s climate. ConnectedGreen is an innovative platform based on smart soil moisture sensors. This platform makes it possible to monitor soil moisture levels in green projects, resulting in less replacement and water usage. Interested in the possibilities? Read more about our solution here.

Sowing grass is an important part of maintaining your garden. A beautiful green lawn is what everyone strives for, especially as the weather gets nicer. Unfortunately, grass can sometimes be an eyesore because most lawns develop bare patches over time. Naturally, you want to do everything you can to prevent this, so let’s start at the beginning: when is the best time to sow grass? In this blog, we will discuss various factors you should consider when choosing the right time to sow grass.

Author: Isabelle Horneman

The soil temperature as an essential factor.

Temperature is one of the most important factors when choosing the right time to sow grass. Grass seeds require a minimum temperature to germinate and grow. Generally, the ideal temperature for sowing grass is between 10 and 20 degrees Celsius. If the temperature is too low, the grass seeds will not germinate, and if the temperature is too high, germination will be delayed or the seeds may even be scorched.

Ground moisture

Rainfall and watering are also important factors when sowing grass. The grass seed needs to remain moist until it germinates. During dry periods, you should regularly water the grass to prevent the seed from drying out and dying. However, make sure the soil doesn’t become too saturated, as it can cause the grass seed to drown.

How do you prepare the soil?

Another important factor in sowing grass is soil preparation. It is important to cultivate and loosen the soil before seeding. Remove all weeds and stones from the ground and optionally spread compost or manure over the grass to enrich the soil and provide the grass seed with the nutrients it needs to grow.

So when is the ideal time to sow grass seeds?

As you could read above, this depends on several factors. Since soil temperature is the most important factor, it is best to wait until March/April to sow. This is because the soil temperature drops significantly in winter. Soil life comes to a halt, and there is relatively little activity in the soil. You can imagine that the temperature in spring is still not very high. In March/April, the soil temperature has usually risen enough for the grass seed to germinate. However, it is necessary to consider how long it remained cold and what the actual soil temperature is, as it can still be too cold during this time of the year. The ideal time to sow grass is in August and September, as the soil temperature is highest, and there is also sufficient rainfall to keep the soil moist enough. These are favorable conditions for grass seed germination, as mentioned earlier.

If, due to the dry, sunny, and warm nature of the summer, the precipitation deficit increases significantly again this growing season, you can monitor soil moisture using soil moisture sensors and the ConnectedGreen platform. If necessary, you can keep your lawn in top condition by manually irrigating it with the right amount of water at the right time. Drought does not occur overnight but is a process that takes place over a longer period of time. After a few heavy rain showers, the grass may turn green again, but the groundwater level may still be low. Therefore, drought may still persist. It is important to continue monitoring soil moisture, even after a few heavy rain showers.

The drought season has begun, and fortunately, the starting position seems favorable. That is good news because in previous years, drought has had significant consequences not only for our nature, agriculture, and drinking water but also for the economy. For this year, it appears that there is sufficient groundwater and surface water to withstand the drought period well. The groundwater level is higher in many areas compared to previous years.

Author: Isabelle Horneman

We must remain vigilant!

We naturally didn’t expect anything different in the Netherlands, but the KNMI emphasizes that we still need to remain vigilant during this time. During the summer months, there is still a possibility of a precipitation deficit, which can cause groundwater levels to decline once again. Additionally, high temperatures and abundant sunlight can lead to rapid soil drying due to water evaporation. It is therefore important not to be too easily satisfied and to remain alert to developments during the drought season, something we fortunately have experience with by now.

The importance of sustainable and responsible water management

In addition to staying alert, it is also important to remain aware of the importance of sustainable and responsible water management. Only in this way can we ensure that we have enough water to live and work in the future. This means that we need to use water sparingly and invest in restoring the natural water balance. But it also means that we need to continue innovating and developing new technologies to optimize our water management.

Bewust omgaan met Being conscious about water

It is important to be conscious about water. This can be done by residents of the Netherlands, for example, by using drinking water sparingly, such as taking shorter showers and turning off the tap while brushing teeth. But farmers, gardeners, governments, and water boards can also contribute by setting up their irrigation systems in a way that saves water and does not excessively wet the soil. Greenery itself also has a water requirement, and in times of drought and water shortage, greenery can exacerbate the problem. This is where ConnectedGreen can make a contribution. With ConnectedGreen’s soil moisture sensors and monitoring platform, it is possible to measure when your greenery needs water, ensuring that you never give too much water and no longer waste water.

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