。
Even if there are any trees, there are hardly any.
Literal
Tree [topic-は] even-if-existing [almost-ほとんど] not-exist.
たとえ…ても ('even if') is the emphatic concessive frame in Japanese, reinforcing the te-form concessive ~ても. Here the clause is shortened to たとえあっても (using the conjunctive of ある). ほとんどない ('almost not / hardly any') uses the quasi-negative adverb ほとんど to soften an absolute 'none' into 'hardly any.'