[XML] What's the AlienDangerSensitivityMod?

[Protok St]

In the Biomes data there is such a parameter as AlienDangerSensitivityMod.
Can anyone explain what does it exactly influence?

<GameData>
    <Table name="PlanetEffects">
***
        <Row>
            <PlanetType>PLANET_VOLCANIC</PlanetType>
            <AlienDangerSensitivityMod>50</AlienDangerSensitivityMod>
        </Row>