# Spanish-language text classification for environmental evidence synthesis using multilingual pre-trained models

## TL;DR

This paper shows how AI can help include Spanish-language research in environmental evidence syntheses, reducing bias and manual work.

## Contribution

A novel approach using multilingual models and class-weights to build a Spanish text classifier for evidence screening.

## Key findings

- The best model achieved 100% recall, ensuring no relevant Spanish papers were missed.
- Over 70% of irrelevant Spanish documents were filtered out using only titles and abstracts.
- The method uses a small labeled Spanish corpus and handles highly imbalanced data effectively.

## Abstract

Artificial intelligence (AI) is increasingly being explored as a tool to optimize and accelerate various stages of evidence synthesis. A persistent challenge in environmental evidence syntheses is that these remain predominantly monolingual (English), leading to biased results and misinforming cross-scale policy decisions. AI offers a promising opportunity to incorporate non-English language evidence in evidence syntheses screening process and help to move beyond the current monolingual focus of evidence syntheses. Using a corpus of Spanish-language peer-reviewed papers on biodiversity conservation interventions, we developed and evaluated text classifiers using supervised machine learning models. Our best-performing model achieved 100% recall meaning no relevant papers (n = 9) were missed and filtered out over 70% (n = 867) of negative documents based only on the title and abstract of each paper. The text was encoded using a pre-trained multilingual model and class-weights were used to deal with a highly imbalanced dataset (0.79%). This research therefore offers an approach to reducing the manual, time-intensive effort required for document screening in evidence syntheses—with minimal risk of missing relevant studies. It highlights the potential of multilingual large language models and class-weights to train a light-weight non-English language classifier that can effectively filter irrelevant texts, using only a small non-English language labelled corpus. Future work could build on our approach to develop a multilingual classifier that enables the inclusion of any non-English scientific literature in evidence syntheses.

The online version contains supplementary material available at 10.1186/s13750-025-00370-9.