Those who destroy access to the seas are strangling Ukraine.
Ukrainian harbours have been closed since the beginning of the war, and now some important grain export plants and steelworks have also been badly hit by shelling. These include a plant belonging to agricultural giant Bunge in Mykolaiv on the Black Sea and the large Azovstal steelworks in Mariupol. Russian attacks on some of Ukraine's most important export centres are destroying the infrastructure. It will be a long time before supply chains can be rebuilt.
Ukraine generates around 40 % of its gross domestic product through exports. Wheat and corn account for around USD 8bn of this and iron ore for USD 3.4bn. Ukraine is endeavouring to open new rail routes for the sale of goods such as grain, but the volume will not be sufficient. Ukrainian food companies are focussing on securing local supplies as hundreds of thousands are at risk of starvation and are without water and electricity. You can find the data for the main port cities in the report below.
This is also an economic war, as Ukrainian exports consist of metals, chemicals and mechanical engineering. For grain, Ukrainian exports are even relevant for feeding the world's population.
Editor-in-chief of Marineforum in an interview with WELT TV
Editor-in-chief of marineforum Holger Schlüter interviewed by WELT on the strategic importance of the Black Sea Fleet
Facts and figures on the Ukrainian ports
World trade across the Black Sea total
Wheat: 28% via SwMeer: 9% Ukr, 20% Rus
Sunflower seeds: 51% from Ukr.
Sunflower oil: 44% from Ukr.
Barley: 13/13 (Ukr/Rus)
Maize: 14/1
Rapeseed 9/3
Odessa - over 1 million inhabitants
Handling volume 2020:
40 million tonnes of bulk goods (bulk)
25 million tonnes of liquid bulk
Grain, gas/oilcoal,
Shipbuilding
Passengers (5 jetties)
Container terminal (subsidiary of HHLA Hamburg)
Mylolayiv - 480,000 inhabitants
Was the most important Shipbuilding site the Soviet Union - 3 large shipyards
Mechanical engineering and agriculture
Light and food industry
Port of origin of the Black Sea Fleet
Mariupol - 440,000 inhabitants
Steel harbour Azov Valley, Azovmash
but also export mechanical engineering, wheat, building materials
Trading down by 2/3 since 2014
Kerch Bridge 33 metres high - freighters mostly 40 metres high,
Paralysing restrictions by Russia (blockade, lockdown, lengthy controls)
Trading partner South/North America lost
Steel export runs by rail to Odessa
1/5 of the city's population (100,000) are internally displaced persons from the Donetsk region
Berdyansk - 115,000 inhabitants
Industrial centre Asowkabel
Source: WELT, Bloomberg, Wikipedia, Schlüter
English 
German
Moin,
This information (Mikolayiv, ...was the most important shipbuilding location in the Soviet Union) also shows how the creeping deindustrialisation progressed under the Ukrainian state leadership with the oligarchs in charge (one of whom is the predecessor of the current Ukrainian President Poroshenko).
Oligarchs had secured all the large shipbuilding yards; however, since shipyards do not offer short-term profits, but only offer long-term earnings (in some cases shipbuilding periods of several years), all shipbuilding yards were run down.
There are almost no shipbuilding activities at the former large shipyards, if they still exist at all...
Great!