Wasalam
May Allah bless you.
This question is part of a long and complex issue related primarily to some methods of punishments, that are not recognised in the Quran and Hadith.
In a nutshell, the Muslim scholars differ as to whether imposing monetary fines is permissible or not.
On one hand, the likes of Imam Abu Hanifa, his student Imam Muhammad, Imam Shafi’i (in his last verdict), some of the Maliki and Hanbali scholars, are of the opinion that it is not permissible to impose such fines.
On the other hand, Qadhi Abu Yusuf, with other scholars among the Malikis, Shafi’is, and Hanbalis, are of the opinion that it is permissible to impose a monetary fine on a criminal. However, what they also meant is that, after collecting the fine, if it has been established that the criminal has repented, then the authority should reimburse him.
If he hasn’t, or there is no hope for him to repent, then the criminal cannot be refunded.
The issue of monetary penalty is also found within the Islamic finance industry where institutions such as banks, could not impose on customers a penalty fee for late payment, as this would amount to riba (interest). Thus, to mitigate the risk of default and to avoid collecting interest, the customers undertake a unilateral promise to donate to charity a given amount in the event of a delayed payment.
As for fines imposed due to a breach of environmental laws. First of all, it is important to understand that the protection of the environment is a requirement of shariah and a duty on the Muslim community (see article: https://shariahconsultant.com/muslims-and-the-environmental-crisis
Secondly, it can be said that taking reasonable actions against those who contribute towards the environmental degradation, is also acceptable from an Islamic perspective. This would include imposing monetary fines upon the offenders.
The rational behind it is that, the prophet (pbuh) imposed certain forms of financial punishment such as, seizing the property of the person who cuts the trees of Madinah [according to the meaning of hadith narrated in Sahi Muslim]
Secondly, some scholars allow the imposition of certain fines on those who commit certain sins. For example, the Malikis see as permissible, to take away from deceptive vendors, milk and saffron that has been mixed with something else. Then, to sell them and distribute the proceeds into charity.
Therefore, since harming the environment is a sin in itself, the same logic can be applied.
Thirdly, when someone wrongfully damages the property of another person, one of the punishment imposed on the offender is for him to replace the item with something similar. If this is not permissible, then the victim should be compensated with a monetary contribution.
In relation to environmental policies, financial compensation is the most practical form of punishment as the money collected by environmental agencies, will be used to cover the cost of the damages caused by the offending company for example. Such as covering the cost of cleaning a polluted river.
Based on the above, despite the monetary fines, it can be said that studying and applying environmental policy is permissible in Islam. However, as laws and regulations change from time to time, the ruling cannot remain the same either if such laws, are causing even greater harms to societies.
And Allah knows best!