Forest fire monitoring in eucalyptus plantations: what to measure and where

Monitoring forest fire means doing two different things that are often confused: forecasting the risk, so the brigade is ready ahead of time, and detecting the fire, so it can be fought early. Each one uses a different tool. This article covers both, with an emphasis on the first, which is where the farm’s own weather station changes the game.

Forecasting the risk: the weather tells you when fire will catch

Fire depends on dry fuel, dry air, heat and wind. In a planted forest, the fuel is always there (leaves, branches, bark, understory); what changes from one day to the next is the weather. That is why fire danger indices are, at bottom, calculations on weather data.

The 30-30-30 rule. A rule of thumb well known to fire brigades: temperature above 30 °C, relative humidity below 30% and wind above 30 km/h together make for the most dangerous day. It is simple and helps the conversation, but it does not accumulate the dryness of several days.

The Monte Alegre Formula (FMA). The index most widely used by forestry companies in Brazil, proposed by Ronaldo Soares in 1972 from the fire records of the Monte Alegre Farm, in the Brazilian state of Paraná. The FMA adds up, day after day since the last significant rain, the inverse of the relative humidity measured at 1 p.m. The more dry days in a row and the lower the afternoon humidity, the higher the number. The day’s rainfall reduces or resets the running total, depending on the amount. The result is placed into danger classes, from none to very high.

The FMA+, proposed later, adds wind speed, which accelerates the spread of fire.

Why the station has to be on the farm

The FMA is sensitive to the 1 p.m. humidity and to each day’s rainfall. The nearest official weather station may be tens of kilometers away, at another altitude, with different rain. A shower that fell on the town and not on the stand resets the index when it should not. With a station on the farm, the index belongs to the farm, calculated every day without anyone writing it down.

Where to install and what to measure

• In an open area, away from trees and buildings, which distort wind and rainfall readings.
• Temperature and humidity in a radiation shield, at the standard meteorological observation height, between 1.25 m and 2 m above the ground.
• Wind at 10 m height, the World Meteorological Organization standard. In a plantation, this means a tall mast or a large clearing.
• Rain in a level rain gauge, with nothing overhead.

One station per farm is the minimum; large farms or farms with rugged terrain need more than one.

From the number to the alert

The index only prevents anything if it reaches the brigade. The workflow that works:

1. The station measures and transmits; the platform calculates the index for each farm.
2. When the class goes up, a WhatsApp alert goes to the brigade and the manager, once, at the change of level.
3. At high risk: water truck filled and positioned, firebreaks checked, surveillance stepped up and restrictions on activities that create sparks.

Detecting the fire is a different tool

A weather station does not see smoke. For detection there are lookout towers, cameras with image analysis and satellite monitoring of heat spots, such as the Queimadas Program run by INPE, Brazil’s National Institute for Space Research, which is open to the public. The index tells you when to watch more closely; detection tells you where the fire started. For anyone who grows planted forest, measuring the risk on your own land is the part of prevention that depends only on you.

Where IoTData fits in

We build the weather station and the platform that calculates the index and alerts the brigade. Where there is no cellular signal, the data goes by LoRa radio to a point with signal or over the DG satellite network, which also delivers in minutes. See IoT for forestry.

Sources: R. V. Soares, Fórmula de Monte Alegre (UFPR, 1972) and FMA+ (Nunes, 2005); World Meteorological Organization, guide to instruments (wind at 10 m; temperature and humidity between 1.25 m and 2 m); INPE, Programa Queimadas.